etching Stainless steel after post weld Heat Treatment

[siamak]

Hi
One of our subcontractor send us a deviation which describes that a carbon steel Pressure vessel which some of it's nozzles are made from stainless steel shall be PWHT at temperature about 620 degrees of centigrade, and as it is forbidden in our specification to do PWHT on s.s materials; he insist on doing furnace PWHT and then etching s.s nozzles to save time. I wanted to know that if anyone knows any reference about such a thing to remove carbides from surface and also how we can be sure that these action was done well and a new Passive layered established on surface of those nozzles ?
thanks for your consideration

[asdqw123]

thank you ,this is good.