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Ted Mooney, P.E. RET
Pine Beach, NJ
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for Metal Finishing since 1989
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Carbon Content of Cold Rolled Steel Affecting Plating?
Q. Hi people, my customer recently complained to me that my Cold Rolled Steel's carbon content was too high, and therefore affecting the clear zinc plating that was to be done to the material, two coating was needed to be done in order for the plating to be set in , after the first layer of coating , dark patches were still seen and a 2nd layer clear zinc plating had to be done to cover the patches. As far as I know , carbon content of material only affect hardness? or could it really affect the plating? my material carbon content was 3%. please advise thank you
Ryan Chngpoh tat hardware trader - Singapore
2007
A. What steel was specified in the order, and what was actually delivered? Was any ASTM or JIS standard, grade, type or class indicated? A 3% C content indicates cast iron (cannot be cold rolled!) so maybe 0.30% C? If AISI 1018 steel (allowable range 0.14-0.20% C) was ordered but you delivered 1030 (0.27-0.34%), it's your problem.
Commercial steel (CS) cold-rolled steel per ASTM A366 & ASTM A1008/A1008M has 0.15% C (maximum); per ASTM A794 the range is 0.16-0.25% C. With many other standards such as ASTM A505 & ASTM A568, the AISI grade must be given. Low carbon grades have greater formability. Although high carbon steels and even cast iron can be zinc plated + clear chromated, an acid chloride plating process may be preferred over cyanide & alkaline zinc processes.
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.
A. I'd suggest that the most likely cause of the need to replate the job was poor pickling of the base material in the first place. If the scale hadn't been properly removed and the component was processed through an alkaline zinc solution then bare patches would result.
John Martin- Wales
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