TABLE IV—Passivation Strategies to Replace CrVI

• CrIII - Difficult to build thickness on Zn but alloys do allow significant increases in thickness. Colors are different. Fate of CrIII is uncertain. • Organic films - Large variety. Coating thickness, uniformity, and color are concerns. • Inorganics - Salts/oxides of Al, Ti, Mo, W, Co, Ce, Zr, etc. produce colored coatings. Do poorly in salt spray. • Oxides - Silicates, phosphates, etc. Complement CrVI, CrIII, and organic coatings. Cant be used alone. • Organometallics - Stability in water is limited to a few compounds. Very expensive chemicals. • Multiple Steps - Combinations of the above, very promising, capital expense may be involved.

TABLE V—Trivalent (CrIII) Observations

• Salt spray on zinc not quite as good as conventional. • Iridescent colors arent identical to CrVI. • Doesnt repair itself. • Still has chromium. • Salt spray on alloys is very good. • Easy application • Thin, conductive very long lived. • In most respects it is a suitable substitute for hexavalent chromium.

TABLE VI—Trivalent (CrIII) Colors: Iridescent & Black