Undesirable spontaneous copper plating in steel pickle line 1

[baglamas]

Our hydrochloric acid pickle line for hot rolled steel sheet contains copper levels in the area of 30 ppm. Under certain (unknown) conditions copper is plated onto the steel sheet. What parameters can I change to prevent this?

We are going to look for the source of copper, but assuming you can't bring down the copper levels what else can you do?

Is it possible to use a dummy cathode with a DC source so that copper will plate there instead of onto the sheet?

Can any chemicals be added to react with the copper ions without affecting the pickle process?

What if a less noble metal such as zinc is introduced in the bath? Will copper preferentially plate on zinc instead of steel?

Feel free to give me a lecture on the basics of plating cause I'm not an expert Thanks guys

 

[kenvlach]

This is not an uncommon problem; it happens by a displacement reaction because Cu is more noble than Fe. See “Plating Copper in a Steel Pickling Line? “

http://www.finishing.com/132/35.html

The suggestions mostly dealt with eliminating the copper source; although one comment was to run a steel coil through the pickling solution to let the copper plate itself out.

I would favor your idea of electrolytic dummy plating.

There are also inhibitors for pickling solutions which would compete with the Cu for the Fe surface once the oxide is dissolved. Maybe try Pickle Pal from

http://www.columbiachemical.com/

There are chemical and electrical methods for purifying acidic solutions, but none are very applicable to a case with only 30 ppm Cu.

Lastly, do NOT add zinc to an HCl solution; you will get a vigorous reaction, H[sub]2[/sub] bubbles and dissolved ZnCl[sub]2[/sub].

 

[Alaguy]

We are having the same type of problem in our pickle line.

 

[kenvlach]

PRO-pHx is a ‘Acid Life Extender’ product which (if I remember correctly) purifies acid solutions of metals by forming insoluble silicates. Mr. French has emailed me some data furnished by customers: “These files show the Cu, Ni, Cd, Cr, and Zn content of the hydrochloric acids used on 3 plating lines. These acid baths have been purified daily using PRO-pHx (a catalyzed reagent process) and simple filtration. In this job shop, the acids are used for pickling, activating, and stripping of parts and racks.”

David French
P (704)607-0191
F (704)598-1020
davidfrench@pro-phx.com

http://www.pro-phx.com

I suggest discussing your acid and dissolved metals concentrations with this guy. Should you try this product, please give feedback -- I am considering using it.

 

[negotiator]

Spontaneous Cu flash ? Sounds like you are eating Cu line, check for tracks, floor leaks, or wait for the juice to stop flowing in 'that'' circuit. KKRRrrriiiizzzzzzzz......

Negotiator