Unless otherwise specified, an intermediate nickel plate is required on copper base alloys or copper plated surfaces prior to the gold plating. Grade A 90 Knoop max. The color of the natural anodic coating depends on the alloy and the coating thickness. Both are considered clear. Hard anodic oxide coatings find application in the engineering industry for components which require a very wear resistant surface.
Corrosion resistance is a function of thickness.
Has a low coefficient of thermal expansion, and is magnetic. Class 1 For corrosion protection. Does not change the appearance of the base metal. Process purifies surface and therefore improves corrosion resistance. Type II Medium temperature with sodium dichrominate.