be met, it can be counteracted with relatively easy measures, including: Reducing the stress level (the oil and gas specifications provide requirements for maximal stress level in H2S-containing environments). Assessing the aggressiveness of the environment (high chloride content, temperature above , etc.). Selecting the right type of stainless steel: super austenitic such as grade 904L or super-duplex (ferritic stainless steels and duplex stainless steels are very resistant to SCC). Galvanic Galvanic corrosion (also called "dissimilar-metal corrosion") refers to corrosion damage induced when two dissimilar materials are coupled in a corrosive electrolyte. The most common electrolyte is water, ranging from freshwater to seawater. When a galvanic couple forms, one of the metals in the couple becomes the anode and corrodes faster than it would alone, while the other becomes the cathode and corrodes slower than it would alone. Stainless steel, due to having a more positive electrode potential than for example carbon steel and aluminium, becomes the cathode, accelerating the corrosion of the anodic metal. An example is the corrosion of aluminium rivets fastening stainless steel sheets in contact with water. The relative surface areas of the anode and the cathode are important in determining the rate of corrosion. In the above example, the surface area of the rivets is small compared to that of the stainless steel sheet, resulting in rapid corrosion. However, if stainless steel fasteners are used to assemble aluminium sheets, galvanic corrosion will be much slower because the galvanic current density on the aluminium surface will be many orders of magnitude smaller. A frequent mistake is to assemble stainless steel plates with carbon steel fasteners; whereas using stainless steel to fasten carbon-steel plates is usually acceptable, the reverse is not. Providing electrical insulation between the dissimilar metals, where possible, is effective at preventing this type of corrosion. High-temperature At elevated temperatures, all metals react with hot gases. The most common high-temperature gaseous mixture is air, of which oxygen is the most reactive component. To avoid corrosion in air, carbon steel is limited to approximately . Oxidation resistance in stainless steels increases with additions of chromium, silicon, and aluminium. Small additions of cerium and yttrium increase the adhesion of the oxide layer on the surface. The addition of chromium remains the most common method to increase high-temperature corrosion resistance in stainless steels; chromium reacts with oxygen to form a chromium oxide scale, which reduces oxygen diffusion into the