Help Advice Req. t304 stainless steel car exhaust rusting / corrosion please help

Hey guys, I have a Stainless Steel Exhaust made from t304 and it appears to be rusting and or corroding, however I have been told that this is
impossible and I need advise.
I can provide several photographs to show, I need an experts advice on what I'm seeing is true rust/corrosion.
please email me on snipped-for-privacy@yahoo.com with subject rust if you can help and ill send you the photos.
cheers for your help all.
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If T304 was contaminated with steel tooling during its fabrication - general surface corrosion of any steel particles remaining on the formed surface can occur. Also deep pitting can occur at embedded steel chip sites. Stainless Steel should be passified (with nitric, sulfuric or other oxidizing acid) after forming - this removes any ferritic or martensitic steel on the surface and increase the thickness of the stainless steel protective oxide.
Check the pipe using a strong magnet an note how much force required to remove the magnet as compared to a similar know ferritic steel pipe- although cold formed stainless steel is magnetic (unless solution annealed) it is not as magnetic as s ferritic steel pipe or tube.
ED
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I agree with Ed that you likely have a contamination rust staining problem. For a discussion of staining, go and download the Euro Inox publication Pickling and Passivating Stainless Steel at: http://www.euro-inox.org/pdf/map/Passivating_Pickling_EN.pdf
Pittsburgh Pete
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