Summary for activated carbon pitting stainless steel Discussion
Activated carbon pitting stainless steel is the core issue Jeff Spooner raised: a 304 stainless valve seal that works in cement powder is failing quickly in activated carbon, with heavy pitting under a greased lip seal leading to lip seal failure, secondary mechanical seal damage, and bearing problems. He asked for a lower-cost material that could extend life to 12–18 months, noting that stainless is not strictly required and that plastics, bronze, or carbon steel might be acceptable. The thread excerpt provided does not include any replies or a final recommendation, so no solution is stated in the source. The only specific alternative mentioned in the question is 2205 duplex stainless, which Jeff says was recommended to him but without explanation and at a much higher cost than 304.
Q. My name is Jeff Spooner and I co-own a mechanical seal manufacturing and repair facility in Vermont. Most of the seal applications we see here are process fluids in centrifugal pumps in which a 300 series stainless steel holds up very well. Occasional tough applications require Hastelloy C or titanium but certainly not the norm. We recently began manufacturing a valve seal that works in powdered applications such as cement and 304 stainless steel has been the material of choice. Now this same seal has been installed into an activated carbon powder and the 304 stainless steel is being heavily pitted in 2 months or less. The pitting is concentrated under a lip seal where grease is present and this pitting is causing the lip seal to fail and then compromise a secondary mechanical seal and roller bearing. We are looking for a material to make this part from that will increase life to 12-18 months or longer without increasing cost substantially. A stainless steel is not necessary we could use a strong plastic, bronze maybe even carbon steel as we are mainly concerned with rusting at atmosphere and not overly concerned with product contamination. 2205 duplex stainless has been recommended without explanation and is also quite expensive compared to 304 stainless. Has anyone had similar problems with activated carbon or any suggestions on how to address our problem?
Jeff Spooner
Product Designer – Colchester, Vermont, USA
January 13, 2010
 | A. Remember that activated carbon may contain residues of strong chemicals (acids) that are impregnated during its manufacture. Carbon has the highest galvanic potential of all conducting materials. In presence of humidity it will tend to corrode most ANY metallic surface. Look for a non-conductive and corrosion resistant material or coating for your valve, like plastic, or graphite itself. Guillermo Marrufo A. You are more than likely getting galvanic corrosion between the carbon and the stainless. Ciaron Murphy |
A. Carbon is washed with either sulfuric or hydrochloric acid. This residue is corroding the stainless steel. If hydrochloric acid is being used the corrosion will be severe. I would recommend titanium for this application as it will be resistant to both sulfuric and hydrochloric acid. Like the other comments, plastic would apply also, but I am not sure of the strength requirements.
Joe Fox
– Painesville, Ohio
January 24, 2010
Can Activated Carbon cause corrosion in 316SS
Q. We are observing corrosion in 316 SS vessel that is used to mix activated carbon and acetone
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. I expect trace levels of water (<0.3%) in the acetone and the activated carbon will have trace (<.1 ppm) chlorides. The corrosion appears to be only in the bottom dish of the vessel and not the sides. Any idea on root cause? Could it be a galvanic phenomena?
Jim Makuc
engineer – Billerica, Massachusetts, USA
November 6, 2015