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Doomed Hero
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The Trials of Blackwier (PbP, preliminary thread)
December 09, 2008, 01:05:49 AM »
So for a while now I've wanted to explore what life under the shadow would be like for normal people in the occupied lands. The recent discussion about Legate behavior and beliefs has made me decide to stop thinking and start doing. So here's my premise-
The players will be playing regular folks in the town of Blackwier. The town smith, the tavern keeper, the local sheriff, the legate's personal aide, ect.
heroes. Not even the town big-wigs. These are the folks who have to deal with the aftermath when the "heroes" come to town and shake things up.
The way I plan on running this will be fairly episodic. Basically, I'll present a scenario, or a problem, let play run until things either resolve or peter out, then basically fast forward to the next event the town will have to deal with. What happens when a Legate decides your child is to be taken away to become a acolyte, or a sacrifice? What do you do when you find out the family next door has been hoarding food? Stuff like that.
I should be able to accommodate as many players as want to join. If you're interested, these are the things I want from you-
1) A short description of your character and their role in the town.
2) At least one person that they like, and why. (this should be something that would be public knowledge)
3) At least one person that they don't like, and why. (also public knowledge)
4) something they are known for in town, other than their profession.
So to start with, I'm going to present a brief description of the town and few of the major players in the community. This is by no means a complete list. If you can come up with an NPC that you'd like to have in the town, let me know. Also, if there are any modifications to the NPC's I list, that's fine too. Whatever works best for your character. I want to encourage player-created content as much as possible.
Jack Chick, Abdul Alhazred, and Aleister Crowley walk into a bar...
Doomed Hero
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Re: The Trials of Blackwier (PbP, preliminary thread)
Reply #1 on:
December 09, 2008, 01:23:42 AM »
This town of roughly 500 people sits between Eisin and Erenhead, about 100 miles from either. It's off the main road enough to be fairly unbothered, but close enough for heavy tithes to be expected.
The town was once a focus point of the war effort. A large keep sat on top of the tallest, widest hill on the edge of a small forest. The north side of the hill sheered down at an impassible angle, making approach from the forested south the only option for an attacking force. The keep was masterfully built, but stood no chance against the dragons. Now the keep is little more than a slag heap of crumbling melted stone. The fire burned the farmland and the forest for miles around, reducing the trees to bowder and sharpened husks. It was devastating at the time. Now, the soil is quite rich, thought the forest is all but gone. Instead of starting less than a mile from the town, it starts nearly 10 miles away.
The town itself grew up around the old keep. The family that was granted dominion over the land, the Leshters, built their manor on the south side of the hill, below the ruin. The family has been overseeing the land and making sure tribute is delivered to Lord Helrion Baden's boats in Erenhead. They pride themselves on the fact that their holdings have never been short in tribute in over 50 years.
The current Mayor, Madame Leshter, rules with an Iron claw. Her son and his tax men ensure that every family meets their quota. Those that don't have plenty of scars to remind them to work harder.
Recently a Legate named Kamar has come to the town to oversee the production of a new Temple of Shadow. The temple has been under construction for many years, but the legates that have come before always seem to be called away without notice. Without oversight, the project has been abandoned in favor of more manpower to meet the mayor's quotas.
There has been friction between the mayor and this new Legate because of the number of people that have been pulled away from thier normal lives to help with the temple's construction. The Legate has demanded that the Mayor reduce her expected quotas
by half
. He claims the armies and the nobles can do without a few extra bushels of wheat if it means the temple will be constructed faster. He has been overheard saying that the mayor has no real authority, that all true authority comes from Izrador, and that she would be better of working in the fields with everyone else.
The people have grown to like the changes brought upon by the sour, self-absorbed Legate in spite of his rabid devotion to the temple's construction. The spells and blessings he gives out seem to be worth the increased tension and the squad of orcs that follows him about.
Tere are roumors of a resistance group operating in the nearby hills. The group of the mayor's men that was sent out to investigate a month ago has not returned yet. No one seems to have actually seen these resistors, or even any signs of them, but it's said that a group of goblin slavers was found dead only 40 miles away, and that the last Legate to leave Blackwier never made it back to Erenhead.
The townsfolk have dubbed the resistance leader "the Hunter" and trat him as both a romanticized vigilante and as the Boogyman. Talk of such things is kept to a hush. Legate Kamar had the last person heard talking of the Hunter beaten severely.
Last Edit: December 09, 2008, 02:22:19 AM by Doomed Hero
Doomed Hero
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Re: The Trials of Blackwier (PbP, preliminary thread)
Reply #2 on:
December 09, 2008, 01:24:16 AM »
People of note-
Tosh Kamar
- Sarcosan Legate, obsessed with completing the temple. Self absorbed, aloof, not very observant. Absorbed in old scrolls and books in Erenland history. Believes that service to the shadow is honorable, and believes in fairness for the faithful. Believes that everyone should be given the chance to best serve their god, and that sacrifice is best and most worthy when it is voluntary. Believes the wealth of a community belongs to the community (as long as they are pious). Preaches that claiming nobility or authority is an affront to Izrador, and that everyone should simply accept their place as his humble servant. Also claims that life has no value at all other than to serve Izrador.
Madame Lesher
- Mayor. Technically owns Blackwier and the surrounding lands. She claims to have the blood of old nobility. She primarily gathers tithes to give to the tax collectors. Many people appriciate this because it means they do not have to deal with the tax collectors themselves, but many believe that she is forcing excessively large tithes on the town. She hates Legate Kamar because of his belief that the wealth of a community should belong only to the community (assuming they are faithful and pious).
Val Leshter
- The Mayor's son. Leads the Tithe collection squad. A known sadist. Likes exercising his authority and doling out punishment. When a quota is not met, it is his hand that wields the lash. he knows he is hated, but he arogantly believes his position and his family will protect him.
- Master Builder, mason, architect. Large aging Dornishman. A "don't rock the boat" sort of guy. Has a strange kinship with Caan, the hobgoblin. Has been commissioned to oversee the construction of the new Temple being built in town.
- Blood Mother Orc. Veteran of the mountain. Assigned to guard the legate Kamar. He believes that this post is insulting, but he takes advantage of the supposed lack of threat to indulge in laziness and occasional bullying. Leads his squad of 4 with bitterness and anger. He keeps one of them with Kamar at all times, and allows the others to do what they want. They hate him, but they enjoy his lax attitude and fear his experience. They know they do not dare challenge him.
Yorick Swift Water
- Gnome Adjudicator, responsible for measuring the town's resource production and use. Also makes sure that any needed supplies from outside the town are brought in. Liked by nearly everyone, but distrusted. He has been known to trade favors from townsfolk for special consideration when it comes to passing out supplies. Spends most of his time gone. Leaves his Hobgoblin assistant in town in his stead.
- Yorick's assistant. A Hobgoblin. Hates inefficiency, (and so hates most people) is harsh with farmers whenever he does his investigations, and even when he is gathering their requests. Often asks for proof that what is requested is actually needed. Has an amiable relationship with Dolan. Avoids the Orcs whenever possible, and bows and scrapes to them when they cross paths.
Danner "Dandan" Dandaral
- Formerly an experienced horse-breaker. After he was overheard talking about the Hunter in the tavern, Legate Kamar set his Orc guards on him. His right hand and arm will never be the same, he is blind in his right eye and he has difficulty talking. his wife, Dalia, cares for him now and tries to keep him indoors, but he still longs for the outdoors. he is a daily reminder of what the price of insubordination can be.
Last Edit: December 09, 2008, 02:26:51 AM by Doomed Hero
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Re: The Trials of Blackwier (PbP, preliminary thread)
Reply #3 on:
December 10, 2008, 03:17:32 AM »
Cool...i'm in!
Kessel son of Valender
Kessel is an Erenlander teen, short with broad shoulders and unkempt black hair. His dark eyes almost always look at the ground not far from his feet, and he is rather shy and quiet. Though his parents and older brother are all farmers, he is apprenticing under Dolan as a stone mason, and shows quite a bit of promise in this work. His quiet focus is exactly what is required for the time-intensive precision work of a mason.
Kessel has nothing but utmost respect for Dolan, but views him with too much awe and subservience to consider him a 'friend'. Legate Kamar, however, he views with a great affection. Not only did he give enough work to Dolan to allow him to take Kessel on as an apprentice, but the Legate's presence has muted the effect of Val, the person Kessel despises most in town. Kessel has witnessed so many beatings of his parents and brother at the hands or order of Val for slack in quotas that he has no love for the man (he was spared most of them due to his younger age, but that didn't mean he couldn't hear their cries). And now Val has taken a barbaric interest in Kessel's younger sister Marnarie. Even if he didn't fear Val as much as he hated him, his natural inclination toward passive obedience would prevent him from doing anything overt against him, but he does hope the Legate will soon dispose of him.
Kessel is known around town for his strong back and willingness to help others unquestioningly. He doesn't have the sharpest mind and doesn't ask questions when others request help, which could quickly put him in situations far out of his experience or control should anyone try to take advantage of him, but so far this hasn't happened.
Dunkin stats
Bane of Legates
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Re: The Trials of Blackwier (PbP, preliminary thread)
Reply #4 on:
December 10, 2008, 12:56:34 PM »
Sounds like a plan, let 's do this thang. Let me know if I can get away with this.
An Erenlander in his late twenties, tall and wiry. His lightish brown hair is worn long and tied back, mostly out of a disinterest in sitting around long enough to cut it, and it often gets in the way of his pale green eyes. When he was still very young, his father was taken by disease - bonerot plague, or so they told him. Since then, his mother Rani did her best to bring him up alone, but it wasn't an easy life.
Fortunately for the both of them, Danner Dandaral took an interest in the boy's life. He taught Toren a little about horses, and helped out when he could, although on occasion Rani did worry about Dandan's tendency to talk more than he ought to.
As Toren grew, he started to take an interest in the herbalist's trade, which was heartily encouraged by both his mother and Danner. Danner showed him how to move around in the forest, and on hs own, Toren slowly learned It had been a long time since the village had anyone who knew much about healing or herbs, and slowly, the sick or injured started to make their way to Toren. He kept this as quiet as he could, not sure how the Legates would take it, but mostly, they seemed to ignore him - a healthy populace can work harder.
Then one day, Dandan let his mouth flap too much around the wrong people, and was beaten nearly to death. It was time to return the favor, and Toren found himself helping Valia as much as he could. Watching his friend and mentor suffer, Toren found a slow resentment starting to burn in his heart for the person who did this to him - the Hunter. If that idiot wasn't running around in the hills stirring up trouble, none of this would've happened.
Toren's usual nervous energy started to get the best of him at this point, and he took to longer than usual outings in the forest, trying to burn some of it off. It's gotten to the point, these days, where the other villagers have started to nervously joke about his wanderlust.
"You want me to what?! ... Gimme a minute."
Dorin's combat data
Dorin's character sheet
Doomed Hero
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Re: The Trials of Blackwier (PbP, preliminary thread)
Reply #5 on:
December 10, 2008, 02:40:18 PM »
Pheros- Looks great. How old is your sister, what's she like, and what's her role in town?
Sholano- Also great. I'd like to make your mother, Rani, the town midwife/healer. This would give a reason for you to take up herbalism.
Give me a few more details about your NPC's and I'll add them to the town roster. Maybe others can use them in their character's stories too.
Bane of Legates
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Re: The Trials of Blackwier (PbP, preliminary thread)
Reply #6 on:
December 10, 2008, 03:23:36 PM »
Excellent. I wasn't sure how healers stood in Midnight villages, that's the only reason I didn't do that myself. Quick rundown follows.
Vaguely Irish-looking woman, a bit worn-looking, but probably pretty in her prime. Her failure to save her husband's life weighs heavily on her, even now, and that's part of why she taught what she could of healing to her child. She tries to keep her spirits up to deal with her energetic son, but as she's growing older, a deep sadness is starting to permeate her demeanor - especially now that Toren has more or less taken over as town healer.
Doomed Hero
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Re: The Trials of Blackwier (PbP, preliminary thread)
Reply #7 on:
December 10, 2008, 03:29:55 PM »
Looks good.
Note to other interested folks, I'm not adverse to people playing "bad guys". Even hobgoblins, orcs or apprentice legates would be ok. This is a game where a mixed-alignment PC group would be just fine.
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Re: The Trials of Blackwier (PbP, preliminary thread)
Reply #8 on:
December 10, 2008, 04:59:01 PM »
Marnarie is about 11 years old, and starting to mature as a woman, meaning that Val is looking at her as a potential bride. Up until now she has spent most of her time helping out around the family's house cleaning, cooking the little food they have, and just making it moderately livable, so that their parents, as well as their older brother Chel can work their alloted fields to produce for quota. Valender (their father) completely disapproves of Val's interest in Marnarie, but cannot say anything outward against it for fear of Val and his men's wrath. He's hoping another in town will take an interest in her and act before Val does anything, but he can only bide his time. For her part Marnarie dislikes Val but doesn't fully comprehend his intentions toward her. When he comes around to talk to her she is only grateful that he leaves without lashing any of her family.
Chel is in his early twenties, and will take over the family house and fields from his parents in the future. Quiet and a hard worker, Chel feels heavily the great weight of responsibility thrust on him to keep the family in good standing with Madame Lesher.
Doomed Hero
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Re: The Trials of Blackwier (PbP, preliminary thread)
Reply #9 on:
December 17, 2008, 01:59:23 AM »
C'mon folks. I need more people for this to be fun.
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Re: The Trials of Blackwier (PbP, preliminary thread)
Reply #10 on:
December 23, 2008, 05:26:40 AM »
Orlan Durke
Orlan is a fading spirit. A man in his late fifties, he doesn't expect to see many more winters before he is considered too much of a burden. In his childhood, Orlan's grandfather and guardian after his parent's untimely death, Sem, did him the great disservice of telling him stories of just kings, ages of freedom, and times of plenty. Orlan has lived his life in endless despair, often coming to tears when remembering the miracles his grandfather spoke of in his fairy tales. Sem died at age fifty-four, and told stories of peace until the day he died. Orlan never fell in love. Orlan often wondered why he held on to life, but something kept him. Whether or not he knew it, something about Sem's stories gave him a shred of hope.
Orlan is obedient, but aloof. He does what he needs to do to keep the orcs off his back, but doesn't go out of his ways to make friends. He has a nasty habit of ridiculing his peers for their shallow ignorance and projecting his weakness onto them. Some others in the village remember a day when Orlan was accused of killing a young man without provocation, but many other's vouch for his pure heart.
Orlan can't stand Dolan. He sees him as a souless and spineless puppet, but like his other judgements, tends to only voice them in passing with those he trusts.
he hates and loves Toren, as he sees much of his childhood in him. One of the few people he confides in, when Toren will listen.
Last Edit: January 06, 2009, 04:00:27 AM by Altus
Loyalty. Vigilance. Precision. A swift death to all who oppose the King. This is my mission. This is my life. Until the Sun rises again, Aiden, I am at your side.
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Re: The Trials of Blackwier (PbP, preliminary thread)
Reply #11 on:
January 06, 2009, 03:05:15 PM »
I bump this, for to have it be seen.
One more. Just one more is necessary for a decent game, methinks. Any takers?
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1. Introduction
The corrosion of electrogalvanised steel is one of the major problems in industry. The material could become more resistant to corrosion if a protective conversion coating is applied on top of the zinc layer. The term "conversion coating", as used in the metal-finishing industry, refers to the conversion of a metal surface into a surface that will more easily accept applied coatings and/or provide a more corrosion resistant surface [1] . Conversion coatings for zinc have been in use since the early 1920's and there are several different products on the market [2] - [16] . These layers protect the zinc coating by acting as a physical barrier to the inducing corrosion species (water, oxygen and ions), and corrosion inhibitor. Furthermore, when the surface is scratched or mechanically damaged, enough water is absorbed by the layer to swell and mend the damaged areas (self-healing effect) [17] .
The Cr(III)-based conversion coating technology was commercially introduced in the late 1980's as an earlier attempt to replace the carcinogenic hexavalent chrome from as many metal-finishing processes as possible [18] - [32] . Tomachuk et al. [33] evaluated the corrosion behavior in zinc coatings obtained from a cyanide-free alkaline bath, then subjected to Cr(III)-based passivation treatments with or without sealing treatment and submerged in different electrolytes. The experimental data analysis allowed to infer that the Cr(III)-based conversion treatment with a suitable sealant provides good corrosion resistance. Also, that still performs better attached to a suitable painting system due to an increased amount of white corrosion products covering the surface micro-defects act as a barrier to oxygen and ionic species diffusion through the conversion layer. Furthermore, the Cr(III) layer also decreased the rate of the oxygen reduction reaction during oxidation of the zinc substrate.
As well, among the chromate-free and environmentally friendly pre-treatments developed so far, the application of Zr-based conversion coatings has gained acceptance [34] [35] [36] [37] . They are currently introduced in several industrial applications, such as in the automotive industry. Puomi et al. [38] showed that the Zr-based conversion coatings on galvanized steel and Galfan steel is mainly composed of ZrO2 and their thickness < 50 nm. The ZrO2 has very attractive properties, such as improved resistance to wear and corrosion, heat resistance and good adhesion to metallic surfaces [39] - [50] .
Hinton et al. made the first research on the rare earths salt-based treatments [9] [10] [51] . They found that cerium was effective in reducing the corrosion cathodic reaction. Other authors also investigated the mechanism of corrosion inhibition on zinc treated with Ce salts [52] - [58] . Aramaki [59] proposed modifying the Ce2O3 film usually formed on the treated surface, oxidizing with H2O2. The result was the formation of a highly resistant layer to the 0.5 mol/L NaCl solution. XPS (X-ray photoelectron spectroscopy) analysis showed the formation of a thin film (thickness < 50 nm) containing a small amount of Ce(IV) which is derived from the oxidation of Ce(III) by the H2O2. The coexistence of Ce(IV) is still investigated [60] . Shibli [61] , developed a nanoparticulate CeO2 film wherein Ce(NO3)3∙6H2O was incorporated into the zinc bath. The coating produced had a thickness of 50 µm; however the thickness of the CeO2 film was approximately 20 nm to 40 nm. Hamlaoui [62] investigated the electrodeposition of layers obtained from electrolytes based on cerium salts on galvanized steel. He found that the more concentrated solution to lower its pH and, therefore, working in highest concentration was vigorous bubbling confirming the presence of large amounts of H2↑. However, if the film was treated with cerium PEG (polyethylene glycol) after passivation, this reduced the number of cracks in the deposit by reducing the hydrogen present in the aqueous medium or by decreasing the film thickness. Montemor et al. [63] and Ferreira et al. [64] have studied the effect of treatment time on the chemical composition and corrosion behavior of Ce(NO3)3 conversion coatings for galvanized steel and found that the film composition and thickness change with time.
As an extensive research is still needed to find effective but non-toxic and environmentally friendly conversion treatments for replacing the based on Cr(VI), the aim of the present work was to study the protective performance of: 1) Cr(III) + Zr complex layer; 2) Ce(III) layer; 3) Ce(IV)/Ce(III) double layer; or 4) Cr(VI) chromating (as reference) applied on electrogalvanised steel sheets. For this, replicates of the coated sheets were immersed for 72 h in aerated 0.05 mol/L NaCl or 0.1 mol/L Na2SO4 solutions and their behavior investigated through AC (electrochemical impedance spectroscopy-EIS) and DC (potentiodynamic polarization) electrochemical techniques. The EIS data were fitted and interpreted by means of equivalent electrical circuit models.
2. Experimental Details
2.1. Preparation of Electrogalvanised and Passivated Samples
1) Panels of low-carbon steel (AISI 1010) with dimension of 7 cm × 10 cm and 0.1 cm thickness were degreased in an alkaline solution (based on KOH, triethanolamine and K2SiO3) at 22˚C ± 2˚C, and polarization with a current density of 4 A/dm2 for 3 min. Then, these panels were rinsed in deionized water, subjected to pickling in HCl 1:1 with an iron inhibitor for 1 min, newly rinsed with deionized water, activated in 5% wt ammonium bifluoride solution for 30 s, and rinsed once more in deionized water. Once this step was completed, the steel samples were electrogalvanised using a cyanide-free alkaline bath containing Zn2+ 12.5 g/L, KOH 170 g/L, K2CO3 50 g/L, leveler additive 10 mL/L, brightening agents 1 mL/L, conditioner 10 mL/L. The cathodic current density was 2 A/dm2 operated at 22˚C ± 2˚C for 45 min [32] ; these samples were identified with the symbol (Z).
Immediately after applying the electrogalvanising step, the surface was activated in 0.5% v/v HNO3 solution, pH = 1, for 10 s, rinsed in deionized water, and pretreated with any of the conversion products specified as follows:
2) Blue-colored Cr(III)-Zr(IV)-based conversion treatment (symbol ZCrZr) whose operating parameters were pH = 4.2 (adjusted with 1% v/v NaOH or 5% v/v H2SO4 solutions), immersion in the industrial bath for 30 s, temperature 22˚C ± 2˚C, and mechanical stirring. The passivation bath was composed by hexafluoro silicic acid + trivalent chromium ions + zirconium complexes (commercial product).
3) Pale iridescent colored Ce(III)-based conversion treatment (symbol ZCe) whose operating parameters were pH 3.5, immersion for 30 s, temperature 22˚C ± 2˚C, and mechanical stirring. The passivation bath was composed by 2.5 g/L CeCl3∙7H2O2, 1 mL/L H2O2, and 0.1 g/L H3BO3. The pH = 3.5 (adjusted to with 1%v/v NaOH or 5% v/v H2SO4 solutions).
4) Pale iridescent colored Ce(IV)/Ce(III) bilayer (symbol ZCeD). The first layer was obtained in 1 g/L Ce(NH4)2(NO3)6 solution, and the second one in 2.5 g/L CeCl3, 1 mL/L H2O2, and 0.1 g/L H3BO3. The operating parameters in both passivation baths were pH = 3.5 (adjusted with 1% NaOH or 5% H2SO4 solutions), immersion for 30 s, temperature 22˚C ± 2˚C, and mechanical stirring.
5) Yellow-colored Cr(VI)-based conversion treatment (symbol ZCr6) used as reference samples. The operating parameters were pH = 1.8, immersion for 30 s, temperature 22˚C ± 2˚C, and mechanical stirring. The passivation bath was composed by 4.6 g/L Na2Cr2O7, conductive salt (NaCl), and diluted HCl for pH adjustment.
At finishing the conversion treatments, the samples were rinsed in deionized water and dried for 15 min at 80˚C. All the samples were stored in desiccators at 22˚C ± 2˚C up to their use.
2.2. Thickness Measurements
Coatings thickness was measured using the X-Ray Fluorescence Method, Helmut Fischer mod XDL-B according to the ASTM B568-98 standard [65] .
2.3. Electrochemical and Corrosion Behavior
The corrosion resistance of the conversion coatings was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy in aerated 0.05 mol/L NaCl or 0.1 mol/L Na2SO4 solutions at 22˚C ± 2˚C.
The electrochemical cell consisted of a classic three-electrode arrangement, where the counter electrode was a Pt mesh, the reference a Saturated Calomel Electrode (SCE = +0.244 V vs. NHE), and the tested specimen acted as the working electrode. The area of the working electrode exposed to the electrolyte solution was 15.9 cm2.
The potentiodynamic polarization curves were acquired by a Potentiostat/Galvanostat Solartron 1280 at a swept rate of 0.2 mV/s, over the range ±0.250 V/(SCE) from the corrosion potential (Ecorr). The electrode potentials were stabilized for 10 min in the electrolyte solution before starting each test. The inhibitive eficiency (E%) was calculated from the following equation [66] :
jcorr-0 is the corrosion current density of the bare galvanized steel sheet; and
jcorr-i is the corrosion current density of the galvanized steel sheet protected by the i-conversion coating.
The EIS tests were performed with a Solartron 1255 Frequency Response Analyser® (FRA) coupled to an Impedance Potentiostat-Galvanostat Omnimetra PG-19A®, and both controlled by the ZPlot®. The measurements were performed at the Ecorr in the 105 to 10−1 Hz frequency range, as a function of the exposure time in the electrolyte solution. A sinusoidal signal with 8 mV of amplitude was applied, and the acquisition rate was 10 points/decade. The Ecorr was recorded before and after the finishing point of each experiment to verify that the stationary requirement was obeyed.
The experimental spectra were fitted and interpreted on the basis of equivalent electrical circuits using the software developed by Boukamp [67] . All impedance measurements were carried out with the electrochemical cell inside a Faraday cage to reduce external interferences as much as possible.
Considering that the corrosion resistance of passivated materials depends on the production procedure, each test was performed on three replicates of each samples type, and the reported results in the following Tables and Figures are the average of them.
3. Results and Discussion
3.1. Chemical Physical Characteristics and Thickness Measurements
The identification symbol, description and thickness measurements of the investigated samples are summarized in Table 1. It can be observed that the samples present similar coating thickness. As it was not possible to obtain information about the passive layer thickness, the values shown in Table 1 correspond to the total coating thickness (zinc + passive layer).
3.2. Polarization Curves
Potentiodynamic measurements were performed to study the corrosion behavior of electrogalvanised steel/conversion layer systems in comparison to the electrogalvanised steel sheets without treatment and in contact with aerated 0.05 mol/L NaCl or 0.1 mol/L Na2SO4 solution at 22˚C ± 2˚C. Four coating compositions were studied corresponding to the ZCe, ZCeD, ZCrZr and ZCr6 samples,
Table 1. Identification, description and coating thickness of the tested samples.
respectively. The potentiodynamic curves are shown in Figure 1(a) and Figure 1(b), and both the corrosion potential (Ecorr) and corrosion current density (jcorr) values obtained from the Tafel extrapolation method are collected in Table 2. It also presents the calculated polarization resistance (Rp) and protective efficiency percentage (E%)values offered by each of the investigated samples.
Potentiodynamic curves obtained in aerated 0.05 mol/L NaCl solution for all the tested surface conditions are displayed in Figure 1(a). The results show similar anodic and cathodic characteristics for the bare zinc coating (Z), or those covered ZCe or ZCeD conversion layers, with a slight polarization of the cathodic reactions and a strong dissolution tendency in the anodic ones. For these samples type, the main cathodic reaction (oxygen reduction) produces OH− ions,
Figure 1. Polarization curves for the electrogalvanised samples without or with surface passivation treatments. Electrolyte: (a) 0.05 M NaCl solution; (b) 0.1 mol/L Na2SO4.
which react with the Zn2+ coming from the anodic areas to form zinc corrosion products. These, combined with the Cl− electrolyte ions, lead to the formation of Simonkolleite and/or other zinc-chloride charged ions [68] [69] and, as a consequence, to a certain diffusional controlled tendency, which indicates that in Cl− medium these sample types are more inclined to inhibit the cathodic reaction due to the high water permeability and porous nature of the protective layers [70] [71] [72] [73] . Both the pure zinc coating and the conversion layers defects lead to anodic depolarization, whereas the conversion layer deposition on partial substrate areas would be the reason for the slight cathodic polarization reaction on the ZCe and ZCeD samples.
On the contrary, the anodic and cathodic branches of the ZCrZr and ZCr6 samples presented significant differences regarding the above tested samples. The Ecorr value of the chromium treated samples was comparatively more negative than the measured in the other ones. Their potentiodynamic curves show that after an active dissolution the ZCrZr and ZCr6 samples revealed a passive behavior until approximately −0.96 V/SCE when the passive film formed on both sample surfaces was broken causing the restarting of the substrate active dissolution. As well, the cathodic polarization curves of the ZCr6 samples indicated an activation control, while the corresponding to the ZCrZr samples was very different.
The results also show that the reaction mainly depolarized by the chromate formed passivating film was the cathodic one. A comparison of the ZCrZr and ZCr6 treatments reveals that the first was related to much lower anodic or cathodic current densities and presented a corrosion potential whose current density (<10−6 A∙cm−2, Table 2) is typical of passive materials. This indicates that
Table 2. Electrochemical parameters obtained from polarization curves.
potential instabilities due to environmental changes in the potential range until passive film breakdown does not lead to highly corrosive and harmful conditions once the passive film stays on the surface, showing that it is a highly protective film. The lowest anodic and cathodic current densities associated to this type of sample show that the conversion layer polarizes the anodic and cathodic reactions, although its breakdown resistance was like the ZCr6 coating. The high corrosion protection that the ZCrZr film afforded to the substrate could be due to the Zr component, however, the Cr3+ component plays an important role contributing to the enhancement of the barrier properties.
Polarization curves obtained in aerated 0.1 mol/L Na2SO4 solution at (22˚C ± 2˚C) for all the tested surface conditions are presented in Figure 1(b). As seen in Figure 1(a), de DC data obtained on zinc (Z) and coated samples (ZCe or ZCeD) confirm that these conversion layers do not significantly affect the electrochemical behavior of the electrogalvanised steel. Therefore, it is possible to assume that the Ce-based conversion layers produced in both cases cannot protect the electrogalvanised steel as a barrier. On the contrary, the ZCrZr and ZCr6 samples show a noticeable jcorr decrease, Table 2. In that sense, the anodic and cathodic characteristics of ZCrZr and ZCr6 samples presented large differences from the Z ones. As seen, reduction of the anodic slope and shifting of Ecorr towards more cathodic domains occurs. The higher barrier properties provided by the ZCrZr coating can be ascribed to both the stability and presence of Cr2O3 and Zr complexes, respectively.
3.3. Impedance Measurements
Examples of the impedance spectra in Bode form obtained at different exposure times in aerated 0.05 mol/L NaCl or 0.1 mol/L Na2SO4 solution at (22˚C ± 2˚C) are shown in Figure 2 and Figure 3, respectively.
Figure 2 displays the impedance evolution of electrogalvanised steel samples, either without or with passivation treatments, after potential stabilization in aerated 0.05 mol/L NaCl solution. Two time constants were indicated in the impedance spectra of the untreated electrogalvanised sample, the one at the higher frequencies (HF) likely due to the presence of zinc corrosion products, and the one at the lower frequencies associated to charging of the electrochemical double layer in parallel with the charge transfer processes at the zinc/solution interface. The HF time constant dislocated into lower frequencies with the immersion time, due to the slowing down of the dissolution processes as result of the increasing zinc corrosion products formed on the electrogalvanised surface. Similar effects were obtained for ZCe or ZCeD samples, however, for these last samples types, the second time constant at lower frequencies are not well defined. Besides, the electrochemical response of a Ce conversion layer, usually seen at high frequencies was not identified on neither of the two types of the tested Ce surface coatings.
The impedance spectra for ZCrZr samples show higher impedance values
Figure 2. Effect of immersion time in naturally aerated 0.05 mol/L NaCl solution on the Bode plots of the tested samples at (a) 0 d; (b) 1 d; (c) 2 d; and (d) 3 d.
Figure 3. Effect of immersion time in naturally aerated 0.1 mol/L Na2SO4 solution on the Bode plots of the tested samples at (a) 0 d; (b) 1 d; (c) 2 d; and (d) 3 d.
associated to these samples compared to the other tested surface treatments, and the protection afforded lasted for longer periods than for the previous ones. The protection afforded lasted for at least 1 d and deteriorated between 1 and 2 d in the exposed ZCrZr samples, whereas for the ZCr6 samples the protection afforded increased with time until 1 d, likely due to precipitation of protective products on the surface, characteristic of this type of layer, being fairly stable until 3 d when the test was concluded. For these two treatments, two times constants were identified, being clearly separated for the ZCr6 samples. These results show that the protection afforded by the Cr(VI) conversion layer not only was greater than the provided by the ZCrZr layer containing trivalent chromium and fluorzirconium particles, but also offered longer duration.
Figure 3 exhibits the evolution of the electrogalvanised steel samples impedance spectra, either without or with passivation treatments, after potential stabilization in aerated 0.1 mol/L Na2SO4 solution. This Figure shows that the ZCrZr and ZCr6 samples provided the largest impedance (over almost the frequency range) while the Z, ZCe and ZCeD samples presented lower and very similar impedance values for the 3 days of immersion. Also, in this electrolytic medium the Bode diagrams show at least two well-defined time constants at the different immersion times tested. However, the deconvolution of these diagrams through the fitting program showed that, in some cases, there were overlapping time constants (not detectable by naked eye), which is why their number could be greater than 2. In accordance with the results obtained in the DC tests, the higher barrier properties provided by the ZCrZr coating can be ascribed to both the stability and presence of Cr2O3 and Zr complexes, while the corresponding to the ZCr6 samples to the effective passivating action offered by the Cr(VI)-based bath.
In this study, the impedance data of pure zinc coating, and the Cr(III) + Zr complex layer, Ce(III) layer, Ce(IV)/Ce(III) double layer or Cr(VI)-treated surfaces can be fitted by the complete or partial version of the equivalent circuit proposed in Figure 4. In this equivalent circuit, Rs represents the electrolyte resistance, R1 the resistance to the ionic flux in the pore and C1 the dielectric capacitance of the conversion layer. The R2 and C2 parameters account for the charge transfer resistance and the electrochemical double layer capacitance of the corrosion process, respectively [19] [74] . As immersion time and zinc dissolution increases, corrosion products could accumulate at the bottom or within the pores. In such circumstances, their contribution to the system impedance would be characterized by the R3 and C3 parameters [19] [74] - [80] . The diffusion component W obtained at certain exposure times was associated with an oxygen diffusion-controlled reaction usually found in zinc corrosion [81] [82] .
The values of the R1, C1, R2, C2, R3, and C3 parameters estimated from the analysis of the impedance spectra fitting as a function of immersion time in 0.05 mol/L NaCl or 0.1 mol/L Na2SO4 are reported in Figures 5(a)-(e) and Figures 6(a)-(g), respectively.
Figure 4. Equivalent circuits used to model the experimental impedance data of the tested samples as a function of the immersion time in naturally aerated 0.1 mol/L Na2SO4 or 0.05 mol/L NaCl solutions.
Figure 5. Time dependence of the resistive-capacitive components of the impedance corresponding to the tested samples immersed in naturally aerated 0.05 mol/L NaCl for 3 d.
3.4. Evolution of Samples, Ecorr and Impedance Components with the Immersion Time
Figures 5(a)-(e) show the evolution of the Ecorr and each component of the equivalent circuit as a function of immersion time of the bare or coated electrogalvanised steel sheets in contact with naturally aerated 0.05 mol/L NaCl solution.
Figure 6. Time dependence of the resistive-capacitive components of the impedance corresponding to the tested samples immersed in naturally aerated 0.1 mol/L Na2SO4 solution for 3 d.
As previously mentioned, the poor barrier properties provided by the conversion layer made possible that the zinc corrosion reaction initiated just after immersion. In general terms, the displacements shown during the immersion test by the Ecorr values corresponding to the different samples can be attributed to the following effects: the decrease of such values were caused by the activation of the zinc areas at the bottom of the conversion layers defects (micropores, microcracks) due to their interaction with the Cl− ions present in the electrolyte. The activation mechanism includes the replacement of the outer part of the zinc oxides by zinc corrosion products, which are less protective than the original oxides. This change enhances electrochemical reactions such as the zinc anodic dissolution. On the contrary, the displacement of the Ecorr values towards nobler values observed for the different samples can be associated to the delay or polarization of the surface reactions between the electrochemically active areas of zinc and the electrolyte due to certain protective capacity developed by the corrosion products on the zinc surface and/or within and at the bottom of the conversion layers defects. This is to attenuate the zinc dissolution rate (anodic reaction) and/or the diffusion of oxygen to cathodic zones.
The results obtained from the fitting procedure described in the above paragraph are shown in Figures 5(b)-(e). The chi squared (χ2) value for the fitting was ≤5 × 10−4 (the smaller this value is, the closer to fit to the experimental data).
Suzuki and Venkatesan [83] [84] studied the corrosion products of zinc in Cl− media. According to these authors, zinc is always covered by a ZnO layer and, depending on the environment humidity, Zn(OH)2 may also be present, which act as a protective barrier preventing corrosion. During the exposure to the aerated 0.05 mol/L NaCl solution for 72 h one interesting observation was that the corrosion of the Z samples was reasonably localized, i.e. it started at small areas and then it changed from side to side along the surface. The corrosion process started with the attack of the zinc oxide/hydroxide barrier by the action of H2O and Cl− ions and zinc dissolution occurred not in uniform way, but in local areas.
The more interesting data to discuss are the resistance of the chemical conversion layer R1 (giving information on the barrier properties of this layer) and the charge transfer resistance R2 (giving information on the kinetic of the corrosive process). An example of evolution of the coating resistance (R1) for the Z samples is in Figure 5(b). The same Figure shows that the resistance provided by the ZCrZr and ZCr6 pretreatments offers a higher protection, in comparison with the ZCe and ZCeD pretreatments.
Particularly for the ZCr6 samples along throughout the test, and for the ZCrZr for the first day of immersion, this fact has a strong influence on the charge transfer resistance and therefore on the corrosion rate (Figure 5(d)). Generally, the decrease of R1 (Figure 5(b)) and increase of C1 (Figure 5(c)) indicates that the blocking performance of the conversion layer has been gradually disappearing [17] [85] . The decline of the anticorrosive performance is attributed to local microcracks formed on the conversion-coating layer. Comparing with the initial stage, the microcracks have propagated throughout the coating surface during the immersion. On the contrary, the trend of the resistance inside the defects (R1) to show certain increase and/or of the coating capacitance (C1) to decrease can be related to the formation and gathering of the zinc corrosion products.
During the same testing time, the evolution of R2 values (Figure 5(d)) reflect the variability of the active surface where corrosion occurs and, hence, the protection effectiveness. In that sense, it is remarkable that passivation-activation can occur simultaneously on the zinc surface with different extension. The higher protection efficiency for the 3 days of immersion was provided by the ZCr6 pretreatment due to the passivation action of the mobile Cr6+ ions available in the coating, followed by the ZCrZr whose protective action has been attributed to both the Zr and the Cr3+ components, as it was established when discussing the results with DC. On the other hand, the R2 values in the ZCe and ZCeD samples dropped drastically during the first day of immersion but then remained almost constant until the end of the test. In all the cases, the presence of a plateau region during the test indicates that a dynamic equilibrium between the anodic and cathodic reactions is reached and suggest a lateral surface coverage of the conversion coating.
The increasing of R2 means that the charge transfer resistance between the zinc and the solution becomes more difficult due to the passivation property afforded by the corresponding conversion coating layer during the immersion. The decreasing of R2 indicates a progressive drop of the protection provided by the conversion layer. The C2 values (Figure 5(e)) are proportional to the area involved in the electrochemical reactions, i.e., the area of microcracks in contact with the solution. Therefore, an increasing indicates that the corrosion inside the microcracks becomes more severe and the microcracks area increases with the immersion time.
Figure 6 shows the evolution of the Ecorr (a), and of each component obtained from the impedance data deconvolution (b-g) for pure or coated electrogalvanised steel sheets immersed for 3 days in naturally aerated 0.1 mol/L Na2SO4 solution. As seen in Figure 6(a), in comparison with the changes in the Ecorr values obtained for the samples tested in contact with NaCl, the measured for their replicates for the same testing time in Na2SO4 solution were much less important. In this case, the most significant displacement (±0.060 V/SCE) occurred in the ZCeD sample, while in the rest, a shift mostly towards slightly more positive values took place. This shift is concern with a slow increase in the amount of corrosion products within the conversion layers defects, which act as a diffusion barrier to ions such as through the conversion layer. However, with the increasing of the immersion time it can be expected that the corrosion inside the defects of the conversion layer become more severe and the cracks occurs, this was may be what happened with the ZCeD samples. Another possibility is that the corrosion products inside the defects loosened and diffuse towards the solution. In this case, the barrier effect is lost, and zinc dissolution is increased, generating new corrosion products and, therefore, a new barrier effect that reduces the electrochemically active areas making that the Ecorr moves towards nobler values.
In Figure 6(b) it is possible to note an increase of the conversion layer resistance (R1) values along the 72 h of immersion for the Z, ZCe and ZCr6 samples. On the contrary, those corresponding to the ZCeD and ZCrZr ones decreased within the first 24 h but then remained constant up to the end of the test. As seen, the R1 values were mostly greater for the Z, ZCe and ZCr6 than those for the ZCeD and ZCrZr samples. Despite this, the charge transfer resistance (R2) (Figure 6(d)) values not only for the ZCr6 but also for the ZCrZr samples were greater than those for the ZCe and ZceD samples, and all of them higher than for the Z ones. This means that to a greater or lesser extent all the conversion coatings were able to reduce the zinc corrosion rate throughout the test. It is assumed that the particularly anomalous behavior of the ZCrZr samples, this is low R1 but high R2 values, could be because the local microcracks formed on this conversion layer do not affect its very effective passivating effect.
The dielectric capacity (C1) evolution for the pure zinc (Z) and the four conversion films tested is shown in Figure 6(c). In this the C1 value remained nearly constant for all the samples, but also that it was almost two orders of magnitude smaller for the better and more protected ZCr6 and ZCrZr samples. This consistency throughout the test was attributed to the fact that once the conversion layer microdefects were full of solution, both the microdefects number and size as well as the dielectric constant value of the electrolyte accumulated inside them remained unchanged.
The electrochemical double layer capacity (C2) initially increased with the immersion time but then remained almost stable for the Z, ZCe, and ZCeD samples, Figure 6(e). As occurred with the coating dielectric capacity (C1), the C2 value was less for the ZCr6 and ZCrZr than for Z, ZCe, and ZCeD samples. The C2 value is proportional to the area involved in the electrochemical reactions, i.e. the area of microdefects in contact with the electrolyte. Therefore, changes in C2 indicate that the corrosion inside of such microdefects become more severe if the electrochemically active areas increase, or else that these latter decrease due to the gathering of corrosion products within and/or the bottom of those microdefects. Finally, another possibility is that its value remains constant if the anodic areas/cathodic areas ratio does not change, as mostly occurred in the case of the ZCr6 and ZCrZr samples.
The time constant (R3C3) at the lowest frequency region corresponds to the corrosion products formed in the micropores or microcracks of the conversion layer. Its presence indicates that the conversion coating has been penetrated by the corrosive medium and corrosion reacts on the zinc coating. Again, the stability over the time as well as the higher R3 and lower C3 values (Figure 6(f) and Figure 6(g)) evidence that the conversion layer based on Cr(VI) provided the best protective behavior against the pure zinc corrosion in such an aggressive environment for this last metal as it is that containing ions. Figure 6(f) also shows that except at the beginning of the test, after 24 h of immersion in 0.1 mol/L Na2SO4 solution, the resistive behavior of the corrosion products formed in the Z, ZCe, ZCeD, and ZCrZr samples was similar and constant. As it happened with the evolution of the parameters discussed in the previous paragraphs, the R3 values stability is indicative that, for these exposure conditions, the corrosion process as well as the blocking action exerted by the corrosion products reached a steady state that lasted until the end of the test. The contribution of the corrosion products capacity (C3) to the impedance of each tested sample is shown in Figure 6(g). As seen, the C3 values did not change significantly; this suggests that the surface area of the corrosion products in contact with the electrolyte neither did it throughout the 72 h of immersion. According to the results obtained with all the resistive and capacitive parameters contributing to the impedance measured for each sample as a function of the immersion time, after a short time of initiation the corrosion processes developed in each of them reached a relative and permanent steady state.
4. Conclusions
The potentiodynamic polarization and EIS techniques allowed the evaluation of the protective efficiency for the tested systems, which was different depending on the conversion layer formulation used to protect the electrogalvanised steel sheets.
The electrochemical behavior of the coated electrogalvanised steel sheets under immersion conditions could be modelled using a different number of time constants hierarchically distributed considering the presence of the conversion layer and both its microcracks and the corrosion products deposited in them. The high frequency time constant (R1C1), was related to the dielectric properties of the conversion layer; the second time constant (R2C2) refers to the zinc corrosion process, while the third one (R3C3) was associated to the presence and dielectric behavior of the zinc corrosion products. The evolution of these parameters pointed out that: 1) in contact with the 0.05 mol/L NaCl solution the higher protection efficiency was provided by the ZCrZr-based coating (96.32%) followed by the ZCr6-one (86.45%), while the less effective corresponded to the ZCe and ZCeD-based coatings, 13.82% and 15.79%, respectively; and 2) in the 0.1 mol/L Na2SO4 solution, the afforded protection degree by the ZCrZr and ZCr6 coatings was again very significant, 96.24% and 98.16%, respectively, but almost negligible (4.80%) by the ZCe-one. An opposite effect to the expected one presented the ZCeD coating since its presence accelerated the corrosion rate of the base substrate by an estimated value of 15.2%.
Although the presence of chromates, particularly those based on hexavalent chromium Cr(VI), remains at the forefront as a corrosion inhibitor of the steel family, the intense research carried out in different laboratories around the world to replace them with other types of coatings being more friendly to the human health and the environment is providing more and more encouraging knowledge. As examples of this, results produced by studies like the one here presented show that new and complex formulations based on a range of rare-earth metal (La, Y, Nd, Gd) salts were shown to be good corrosion inhibitors, acting by reducing the cathodic oxygen reduction reaction. In the same way, organic carboxylate compounds (such as salicylate and cinnamate) at relatively high concentrations, were found to be efficient anodic inhibitors by forming a protective layer, mainly at the anodic sites.
The authors acknowledge the Brazilian research agency FAPESP (Process 2015/0995-2 and Process 2016/50454-6), Comisión de Investigaciones Científicas de la Provincia de Buenos Aires (CICPBA), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), and Universidad Nacional de La Plata (UNLP) of Argentina for their financial support to this research.
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text:
To make Ina's banana muffins crunchy on top, top them with dried banana chips, granola, or and coconut!
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Banana Crunch Muffins
Level: Easy
Total: 45 min
Prep: 20 min
Cook: 25 min
Yield: 18 large muffins
3 cups all-purpose flour
2 cups sugar
2 teaspoons baking powder
1 teaspoon baking soda
1/2 teaspoon salt
1/2 pound unsalted butter, melted and cooled
2 extra-large eggs
3/4 cup whole milk
2 teaspoons pure vanilla extract
1 cup mashed ripe bananas (2 bananas)
1 cup medium-diced ripe bananas (1 banana)
1 cup small-diced walnuts
1 cup granola
1 cup sweetened shredded coconut
Dried banana chips, granola, or shredded coconut, optional
Preheat the oven to 350 degrees F.
Line 18 large muffin cups with paper liners. Sift the flour, sugar, baking powder, baking soda, and salt into the bowl of an electric mixer fitted with a paddle attachment. Add the melted butter and blend. Combine the eggs, milk, vanilla, and mashed bananas, and add them to the flour-and-butter mixture. Scrape the bowl and blend well. Don't overmix.
Fold the diced bananas, walnuts, granola, and coconut into the batter. Spoon the batter into the paper liners, filling each 1 to the top. Top each muffin with dried banana chips, granola, or coconut, if desired. Bake for 25 to 30 minutes, or until the tops are brown and a toothpick comes out clean. Cool slightly, remove from the pan, and serve.
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