High Performance Alternative to Hexavalent Chromium Passivation of Plated Zinc and Zinc Alloys 2001-01-0644
Hexavalent chrome passivates have been used for improving the corrosion resistance of sacrificial zinc and zinc alloy coatings on ferrous substrates for many years. However, forthcoming legislation and corporate policies are beginning to curtail the use of hexavalent chrome compounds and replacements are actively being sought.
Comparative corrosion resistance data is presented here. The data shows that the corrosion resistance of the trivalent passivates do not significantly diminish after thermal shock, as is the case with hexavalent chromates. This makes it particularly suitable for components that are subjected to high ambient temperatures.
No changes to the dimensional characteristics of the components occur. Recommended application areas include the engine compartment, brake components, fasteners of all sizes and fluid system components.
When used in conjunction with certain final finishes, these hexavalent chrome free passivates have the potential to replace more expensive alloy or dip spin type coatings.