Zinc coating is what Porsche put on the original bolts. IIRC it prevents corrosion of the bolt edit: from boltscience.com ZINC ELECTROPLATING is a common way to protect threaded fasteners from the effects of corrosion. Zinc electroplating can be completed in acid chloride, alkaline or cyanide baths. Supplemental coatings are frequently applied to zinc electroplating. These coatings, such as zinc phosphate or chromate conversion, provide a protective passivation layer on the zinc which assists in reducing the corrosion rate. |
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