Testing of stainless steel welds

[manxJim]

We have hade some frames made from 304 stainless steel which then have been powder coated
We suspect that some of the welds have been done with mild steel filler rod
Is there a quick way to check if mild steel has been used?
Someone has suggested testing the welds with a magnet, would this be reliable? Some welds on the frames are more magnetic than others
Thanks

 

[metengr]

Yes. If possible, remove the powder coating to expose only the weld metal surface, a check with a small magnet should work. A strong attraction will be felt if the weld was deposited with carbon steel filler.

Stainless steel welds will exhibit a very mild or weak attraction because of the ferrite content in the weld deposit.

 

[ijzer]

you could use coppersulphate . it turns brown on mild stel.

 

[CWIC]

A 5% nital acid solution will provide a sure method for distinguishing between the steel (if present) and stainless materials.