Question

What causes white corrosion?

Answer 1

1. White corrosion or white rust is the white powder that is formed on the surface of galvanized metal objects.
2. The white rust formed can cause significant damage to the surface coating made up of zinc.
3. The reaction for the formation of white rust is
   $2\mathrm{Zn}+2{\mathrm{H}}_2\mathrm{O}+{\mathrm{O}}_2\to 2\mathrm{Zn}{\left(\mathrm{OH}\right)}_2$
4. Zinc is a relatively reactive metal that forms oxides on being exposed to air and moisture.
5. The oxide formed is white-colored and continues to degrade the protective coating of the metal.
6. Thus, white corrosion occurs due to the reaction of water and air (or oxygen) with Zinc metal.