Problem? Solution? Chime right in!
(perhaps the world's last 'no registration' site)
"Phosphating instead of HCl Pickling before Galvanizing"
March 8, 2016
Q. Good morning
My name is Rob Watchorn and I currently operate a Hydrochloric (HCl) Acid Regeneration facility in South Africa.
At present, all the galvanizers use HCl to pickle their steel prior to galvanizing.
I have been requested to investigate the feasibility of replacing the HCl with a Phosphate based pre-treatment.
I have some concerns relating to how the galvanizing process may be affected by the phosphate coating on the steel.
Any advice or information will be greatly appreciated.
HCl acid regenerator - Johannesburg, South Africa
March 12, 2016
A. I don't think phosphate coating will work at all.
However if your interest is simply to stop the use of HCl, then phosphoric acid will probably work, however:
You will probably need longer contact time = lower line speed.
Phosphoric is more expensive.
Sulfuric acid could probably also work, with the same problems as phosphoric.
Jeffrey Holmes, CEF
Spartanburg, South Carolina
March 13, 2016
Galvanizing Consultant - Hot Springs, South Dakota, USA
March 15, 2016
A. Galvanizing isn't a coating(in the usual sense of the word), it's an alloying reaction. It will only take place between iron and zinc, and only when the iron (steel) is chemically clean.
Westfield, Scotland, UK