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How to wipe the chromic acid after the passivation of galvanized sheet?
July 17, 2011
Dear sir,
We are doing the coating at the cold roll sheet which having the thickness and width 0.60 x1250 mm to 3 x1250 mm respectively.To avoid white rust formation on the galvised sheet, we are doing passivation through chromic acid. After the passivation the excess chromic acid is wiped or squeezed through a roller made of hypalon rubber.
Now a days, we are facing the white rust formation because of galavansed sheet not getting properly squeezed through the roller.
To get of out this problem, we have increase the squeezer roller cylinder size but problem is not sorted out.
So how you can help us for said problem? Is there any way to wipe out the excess chromic acid from the galvansed sheet? or the sqeezing through the roller is ultimate solution.
Is there any technique develop in world to wipe out the chromic acid with high flow and low pressure nozzle like the zinc wiping nozzles?.
Regards
Gajanan Ghugal
steel - Nagpur, India
GALVANISING LINE - NAGPUR, MAHARASTRA & INDIA
August 1, 2011
Basic reason for white rust is wet packing. What I understand the sheet is being quenched in normal water than pass through passivation solution.
Please provide 2 or 3 rows of Hot Air blow through out to sheet width up and down to Sheet after the rubber rollers. And be sure the sheet is properly dried and has come to room temperature before re-coiling.
Hopefully you will be out of problem.
- Mumbai, Maharashtra, India
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