<http://purl.org/dc/terms/description>
"There is an urgent need to develop new non-chromating coating methods for the\r\ncorrosion protection of aluminum alloys, and this thesis reports studies to establish\r\noptimal working conditions for forming zinc phosphate coatings on 6061-T6 aluminum\r\nalloy. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS)\r\nand corrosion tests were used to characterize the treated 6061-A1 surface, and to assess\r\nthe effects of different parameters in the coating bath, as well as different pre-treatments\r\nand post-treatments.\r\nThe initial study investigated different working conditions for the zinc\r\nphosphating, and this built on other studies from this laboratory. An initially considered\r\ncoating bath had 16.0 ml H3P04 (85%), 5.36 g ZnO and 0.5 g NaF per liter, and optimal\r\nconditions for coating involved dipping the 6061-A1 samples into this bath at 60 \u00B0C for 6\r\nmin. But the addition of more fluoride was shown to be effective for increasing the zinc\r\nphosphate coverage on the aluminum alloy; the optimal range of F\" being from 400 ppm\r\nto 600 ppm for these conditions.\r\nBased on the working condition study, the effects of pre-treatments, posttreatments,\r\nand associated procedures involved with the zinc phosphating of 6061-A1\r\nalloy on the quality of the final coating were investigated. Comparisons were made\r\nbetween acid etching and mechanical polishing in the pre-treatment stages, and the\r\nmechanical polishing involved was done by either machine polishing or hand polishing.\r\nNew post-treatment procedures were investigated using methyltriethoxysilane. It results\r\nin a considerable increase in the zinc phosphate coverage and coating thickness on the\r\naluminum surface. This gave a greatly improved corrosion resistance by the coating\r\n\r\ncompared with samples that did not have the silane post-treatment. A related silane\r\ntreatment can also be used at an intermediate stage in the zinc phosphating immersion.\r\nIn order to improve the final coating, Cu\u00B2\u207A and Ni\u00B2\u207A ions were studied as\r\naccelerators. Cu(N0\u2083)\u2082 (0.002 wt%) and Ni(N0\u2083)\u2082 (0.0004 wt%) were separately\r\nintroduced to the basic phosphating baths containing H\u2083PO\u2084; ZnO and NaF, and each was\r\nshown to not only increase the phosphating speed, but also to improve the corrosion\r\nresistance and adhesion, insofar as the coating contained smaller crystalline grains and\r\nincreased coverage of zinc phosphate on the surface. Of these two accelerators, Ni\u00B2\u207A\r\nappeared especially effective at increasing the corrosion protection ability of the final\r\ncoating. Although NO\u00B3\u207B has some capabilities as an accelerator it was shown that its\r\neffect was negligible in this context at the concentrations used."@en
<https://open.library.ubc.ca/cIRcle/collections/ubctheses/831/items/1.0061451>