plating, anodizing, & finishing Q&As since 1989
HOW TO AVOID CHROME SEALING AFTER PHOSPHATING TO AVOID POLLUTION
We generally use chrome sealing after phosphating of ferrous items in C&W Workshop/Eastern Railway/Liluah/India. But pollution department is objecting us to use chrome sealing on the ground that chrome waste will enhance pollution. In this situation what are the alternative methods which we can adopt after phosphating the item?
Carriage and Wagon Workshop/Eastern Railway/Liluah/West Bengal/India - Howrah, West Bengal, India
There are non-chrome passivation chemicals and sealers available from reputed companies in India. These are confirming to very stringent norms, both in India and abroad.Amit Amembal
Dear Mr. P. N. Chakraborthy,
A chromic acid based passivation treatment is given after the phosphating process to -->
1. Remove residual phosphating chemical completely from the phosphated surface;
2. Neutralize harmful dissolved salts in the rinse water;
3. seal any void that may remain in the phosphate coating and
4. forms a chromate coating over the phosphate coating, thus enhancing the corrosion-resistance of the phosphate coating.
A Non-chrome passivation of of the phosphated surface results in -->
a. remove residual phosphating chemical, and
b. remove harmful dissolved salts that may be in the rinse water.
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