The corrosion resistance of zinc can be enhanced by a post plating dip called a passivate

This dip process applies a thin coating onto the surface of the zinc.

Additional coatings can be added to further improve the salt spray performance or to modify the lubricity of the component or fastener by the addition of top coat torque modifiers. These are available in a range of values to suit the majority of automotive specifications from 0.008µm.

YTS AB offers WHITE, YELLOW,  BLACK AND BLUE passivation.

•Yellow Zinc — This type of zinc coating is commonly used in the automotive industry and offers an average level of protection against corrosion.
•Black Zinc — Black zinc coatings are available as a black oxide that can actually be olive-drab in color, or as a pure black coating. The former will normally provide slightly better corrosion resistance.

•Clear or Blue Zinc — This coating formulation tends to offer fewer amounts of corrosion protection, although it’s regarded as being more environmentally friendly.