A patented process of zine and aluminium flake coating, is better option to overcome problems related to ordinary zinc plating once the passivation film wears off. Corrosion is a major problem in autombile components and fasters. This dacrodip sol is a dispersed aqueous sol made out of metallic zinc and aluminium flakes, chromic acid and glycol,etc. The duly cleaned components are dipped into it and dranning and/or spinning remove any excess sol for catina components, are then healed to about 300c in an oven in a closely controlled amosphere. The hexavalent chromium gets reduced to trivalent chromium, i e., an insoluble amorphous oxide. It acts as a binder for the many overlapping flakes of zinc and aluminium to form a film. On same time the chromic acid in the sol also reacts with the substrate forming a chemical bond providing a strong adhesion. This corrosion prevention mechanism of the film comes from the controlled galvanic protection of zinc flakes in the presence of intergral chromate passivation of each and every flake. It can be applied in auto parts like bolts, bolts with captive washers, nuts, engine studs, foundation bolts, washers, clips, coil springs, brackets, connectors, tapping screws, hose clamps, brake discs exhaust pipes, engine compartment components, specially under body components and many marine engine components.
