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Copper Plating Issue
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Dear Sir,
We are doing copper plating on CRCA steel strip of 0.350mm thickness and 300 mm width on continuous copper plating line. We are facing the problem if the plating. I am writing below the details of process and the problems. Kidly advise.
Copper Plating Process :
· Using 11 tank Copper plating process, 7 tank cleaning process, two tanks plating process. · First strike plating tank # 8, having pH 11.04, KCN: 5.2 g/l, CuCN : 21.44g/l, Rochelle Salt: 12.65 g/l, Carbonate : 118.68 g/l. Current : 2000 Amps. Four Current Rollers, 3 bottom rollers, 7 anode baskets, Cu anode in 1¤ dia X 3¤ long pieces placed in baskets, level above the solution level. Tank Capacity : 11,000 l.
· Second Main plating bath # 9, having pH 12.4, KCN: 11.44 g/l, CuCN : 51.82g/l, Rochelle Salt: 15.18 g/l, Carbonate : 143.52 g/l. Current : 3000 Amps. Four Current Rollers, 3 bottom rollers, 7 anode baskets, Cu anode in 1¤ dia X 3¤ long pieces placed in baskets, level above the solution level. Tank Capacity : 11,000 l. line speed 20 ft/min.
Problem :
· Cu thickness not even on both the sides of the strip i.e. upside & down side. One side is 3 times the other side ( checked under microscope). · Average copper coating thickness (checked by chemical stripping method)side of the strip ( strip width 300mm , thickness 0.350 mm) i.e. left & right more. Center 7.15 Microns, Left side 9.1 microns. Right side 9.17 microns. · No peel off, blister problem, adhesion is good.
· Cu anodes do not dissolve, consumption of CuCN high.
. Does copper plating has affect on microstructure of steel strip.
Kindly advise .
SUKHDEV NARAYAN- VADODARA, GUJARAT, INDIA
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It is necessary to consider the amount of free cyanide in the bath. 10 g/l.
Ivan Noguera- Colombia
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Mr Narayan,
Please maintain:
Free cyanide above 12 to 13 GPL. Minimum.
Check that copper Cyanide level is above 18 GPl to 20 GPL.
Reduce Carbonates to 80 GPL
Check current uniformity at every individual busbar with a tong tester in Amps drawn, once a shift.
Increase anode area by 25 % if possible.
Circulate the solution using a pump (not air) against the flow of sheet.
Chemistry and some physical aspects will help uniform deposits.
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