Hard-coat (Type III) anodized aluminum alloys have been used by the military,
aerospace, automotive, and other industries for applications where superior hardness and
wear resistance are required. In recent years there has been a great interest in sealing and
dyeing hard-coated aluminum in order to improve the corrosion resistance and appearance of
the oxide film. Although hard-coated aluminum has very high wear resistance, it has to be
sealed to ensure a desirable level of corrosion resistance. However, conventional industrial
seals for hard-coated aluminum cause a dramatic reduction in abrasive wear resistance. A
novel room temperature trivalent chromium based seal was found to be an excellent posttreatment
for hard-coated aluminum to provide enhanced corrosion resistance without
compromising the wear characteristics. In this study, a comparison of post treatments including
trivalent chromium based seal, hydrothermal, nickel acetate, sodium dichromate, sodium
silicate, nickel fluoride, black dye, black dye and nickel seals was made. The quality of the
oxide film was evaluated by microhardness, wear resistance, corrosion resistance, and
dielectric strength. The effects and possible mechanisms of the post-treatment processes on
the anodic film are discussed.
Keywords: Hard-coat, Anodized Aluminum, Type III, Sealer, Steel