ISO 2081 Designation Codes Code Designation Description Zn Zinc Coating Pure zinc coating applied for basic corrosion resistance on iron or steel. A Transparent Conversion Coating Transparent chromate layer to enhance corrosion resistance. B Yellow Chromate Conversion Yellow chromate layer for improved corrosion protection. D Blue Chromate Conversion Blue chromate layer that provides moderate corrosion … Continue reading ISO 2081 Designation | Metallic and other inorganic coatings — Electroplated coatings of zinc with supplementary treatments on iron or steel