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topic 2997

Hot Rolled vs Cold Rolled Steel

A discussion started in 1999 but continuing through 2017


Q. Being a captive manufacturer, we receive close to 1 million a year of plated product but I see our chrome products finish vary throughout the year. Recently we have run into a roughness problem, our plater claims material is the cause. We use a hot rolled pickled in oil product A-36 steel, the material is double skin passed, stress free, surface quality is superior to a standard a-36 sheet produced in USA; we buy from mills in Japan and France. Steel is pickled to remove laser oxide, polished to remove imperfections, and plated (copper, nickel, chrome). Is there any truth to steel quality creating this type of problem? What's the difference between cold/hot rolled ... they both go through same polishing process prior to plate? Does chemical make-up of the steel (i.e., more or less carbon) affect surface finish? Thanks for any information.

Brian Fletcher
- Gresham, Oregon


A. Anything is possible, but it is most likely that something changed in the electroplating process.

I would first look for:

1. Changes in the polishing step and the alkaline cleaning step for changes in the buffing compounds versus the ability of the alkaline cleaner to remove the compounds. (example: Do some parts get run in an alkaline cleaner before the cleaner is up to temperature?)

2. Copper cyanide baths can cause a lot of roughness if the copper anodes are not dissolving correctly. (example: Bath runs in and out of balance as the day wears on.)

3. Shelf roughness in nickel plating solutions could come from precipitated iron, inadequate filtration etc. (example: iron builds up in nickel plating tank and drops out when pH gets too high.)

It may be too obvious for words, but unacceptable variations in a process are the result of processes that are out of adequate control. Someone must make a decision that your plating process is under control so that you can take your investigations elsewhere.

tom pullizzi portrait
Tom Pullizzi
Falls Township, Pennsylvania




Larry Smith
- Winston-Salem, North Carolina

October 6, 2017

Q. We test the performance of our powder coat line by spraying blanks and then salt spray per ASTM B117 [link by ed. to spec at TechStreet] . I have noticed the Hot rolled pickled and oiled blanks typically outperform the cold rolled blanks. Can somebody explain why I am seeing this?

Troy Hartwig
- Schofield WI USA

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