HOW DO CHROMATE PRIMERS FUNCTION? Q: What does chromate do in the primer? (chromate vs. non chromate formulations) A: Primers that contain hexavalent chromate (Cr+6) are often known for their outstanding ability to retard galvanic corrosion. If a primed piece of steel is exposed to a humid or wet environment a small fraction of the chromate-containing pigment, (such as zinc and strontium chromates) will dissolve and spread on the metal surface immediately below. The steel is passivated (a microscopically thin inorganic coating is formed at the primer/steel interface) and corrosion cannot take place. On dry and non-humid days the chromate pigment performs no corrosion-retarding function, nor is it required, because galvanic corrosion does not take place in the absence of moisture. 
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