DEF & 304 Stainless Corrosion 1

[generalpatton]

Diesel Exhaust Fluid - DEF (32.5% UREA and 67.5% water), PH 8-9.

In the event there is iron embedment contamination in the 304SS from A36 particles, will the urea dissolve the iron and allow for the protective later of 304 SS to form? Or will the layer not be formed and pitting begin to take place, self-feeding the corrosion process between the solution and an unpassivated layer of SS? If the latter, pickling to remove any free iron would be the process to fix the issue?

On a similar subject the weld oxide layer that is formed would likely experience corrosion when exposed to DEF? Thanks for any input.

 

[EdStainless]

I have heard stories of SS tanks that were fabricated with common steel tools and welded with poor shield gas working just fine in DEF, and then I have seen cases where slight weld discoloration was the cause of serious corrosion. None of these were my products so I was not party to further details.
DEF is not going to dissolve embedded iron from SS. You really should pickle before it ever goes into service. Once pits form you can only slow corrosion down, not stop it.

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P.E. Metallurgy, Plymouth Tube

 

[generalpatton]

Thanks for the reply. In the case where severe corrosion was observed was this the 32.5 urea/67.5% water mixture?