plating, anodizing, & finishing Q&As since 1989
Assessing corrosion of Zinc plating during salt spray testing
August 11, 2010
Hello ..My name is Ben and I work for a large manufacturing company in the UK. We buy in many Zinc plated components and as incoming quality check salt spray test them to ASTM B117
My question is what order would you expect to see corrosion products. White, black then red? And why? I know that red is the corrosion of the base material but why do you see white and black corrosion occurring ?
Technician - United Kingdom
August 13, 2010
White corrosion products first, this is corrosion of the zinc. Zinc is sacrificial to steel so corrodes first. The black comes from many sources such as the chromate passivate. Then comes the red corrosion products of the base material.
Aerospace - Yeovil, Somerset, UK