Summary for high temperature discoloration Discussion
High temperature discoloration of stainless steel is the issue here: Anette Rasmussen asked for a cheaper alternative to protective gas for valve parts heated to about 1000 °C for annealing and then water-quenched, because the stainless steel was becoming miss-colored. She wanted a protective coating that could prevent oxidation and asked whether it could be sourced in Europe. The only answer in the thread was brief: a contributor suggested trying ceramic or enamel painting as a possible protective coating, but did not provide product names, performance data, or European supplier details. So the discussion does not confirm a proven solution; it only offers a tentative coating idea for further investigation.
February 25, 2013
Q. As a part of a development project for a manufacturer of valves, we are searching for a high temperature protective coating, which can prevent oxidation.
As a part of the manufacture of the valve, it is heated to approximately 1000 °C, in order to anneal the valve. After the heating the stainless steel is quenched in water. The manufacturer wants to avoid miss-coloring of the valves. The manufacturer have tried protective gas with success, however the expenses of the gas was unacceptable high, and there for they are searching for a cheaper alternative.
Can you recommend us a “protective coating”?
RFQ: Can the product be delivered in Europe, or does the manufacturer have a European representative we can contact?
Best Regards
Anette, Denmark
Anette Rasmussen
Consultant – Lyngby, Denmark
A. What if you tried ceramic or enamel painting? Good luck.
Khair Shishani
aircraft maintenance – Al Ain, UAE
March 3, 2013
A. Anette
Copper plating is used to mask select surfaces from absorbing carbon during carburizing operations. Might work in a vacuum environment also. You would need to strip the copper after your annealing operation. There might be some outgassing from/of the copper plating.
Willie Alexander
– Colorado Springs, Colorado
A. Dear Anette
You experience discoloring due to oxidizing of stainless steel, a situation well known from welding or annealing.
I see 3 possibilities
1. Remove oxygen by the use of protective gases or vacuum
2. Protective coating, which have to be applied and removed
3. Remove discoloring
Since I have no clue of sizes, it is difficult to put up prices, but solution 2 sounds as the most expensive to me.
I guess you need an economic alternative for your costumer, and remove discolor on stainless can be done by pickling. You did not mention the stainless type, so I can not come up with a pickling solution, but some salt of HF is always convenient.
Best regards
Bo Konig
– Aalborg Denmark