Pitting corrosion on stainless steel

[moonshine]

On removal of a vent hose from the stub of a stainless steel holding tank I found that the end of the stub had been 'eaten' away. I also found surface pitting for 10mm from the end of the stub where the hose was clamped. Tank is only 4 years old, and to my knowledge the hose has not be removed before !? The boat builder had used a very rubbery adhesive on the stub, (Sikaflex product ?), where there was adhesion there does not seems to be any corrosion, but the downside was this made disassembly only possible by cutting the hose.

Reading up on the subject, the problem seems to be exclusion of oxygen from the surface of the SS. Difficult to see how this can be overcome with a hose clamped on the stub ?

Do the experts have any suggestions for a product, (apart from Sikaflex), that could be applied to the surface before assembling the hose and would stop/slow corrosion ?

Moonshine

 

[Tranona]

Crevice corrosion does occur when there is a lack of oxygen . However, it is just as likely to be caused by uric acid. Stainless steel is not the best material for a holding tank, particularly if welded construction as uric acid can corrode the welds. Welded or rotationally moulded plastic tanks are the best type for holding tanks.

 

[vyv_cox]

I'm not sure why you say 'apart from Sikaflex' as this is exactly what I would use. Don't believe the myths about never getting the components apart again, as myths is what they are. Clean up the area to be joined carefully with steel wool, as emery cloths can tend to leave greasy deposits.

As Tranona has said stainless steel is far from ideal for a holding tank in seawater systems but excluding the water from this joint will prevent corrosion. You do need to inspect the tank very carefully for any other signs of corrosion, especially adjacent to the welds.