Rust blooms on A240 S40930 material

[qualitypro]

We had A240 S40930 stainless material used by our supplier for the stack liners for exhaust gas. Rust blooms started appearing on the entire length and circumference of these liners after delivery to site. The supplier came back telling this is due to the fact that they did grit blasting in the shop after doing liner installation on the stacks and that surface rust is acceptable for this material as it does oxidize when exposed to exhaust gases. These stacks have been erected and cleaning would be cumbersome. Can somebody say if this is acceptable and if not what should be the corrective action to clean this up?

 

[mcguire]

40930 when used in automotive exhaust applications normally exhibits red rust. It is engineered to just be corrosion resistant enough to not have perforation by corrosion. It is never pretty.

Michael McGuire

http://stainlesssteelforengineers.blogspot.com/

 

[EdStainless]

Yes, 409 is barely stainless. A light oxide finish usually doesn't show rust because it is dark enough to hide it.
It will not impact high temperature corrosion resistance.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube