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Black spots on zinc plating during salt spray test

December 28, 2011

Q. During salt spray test of 5%NaCl solution, I observe black spots after 12 hrs,
is it start of corrosion?
how can I reduce it?
is it serious?
chemical composition of plating material is Sodium cyanide, zinc cyanide and sodium hydroxide.
base metal is MS.
I need your guidance in this regard.

Engr. Muhammad Yousuf Malik
- Lahore, Pakistan

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