coating for bare pipe at supports 1

[MBlackman]

Posted this on a Linkedin group, no response so trying here.
According to one article from a pipe support vendor, corrosion under bare carbon steel pipe at resting supports is initiated when the coating degrades from sitting in contact with trapped moisture for long periods. So even when resting on a non-metallic isolation pad, the mechanism is still there, and may in fact be worse than sitting on steel as the pad indents and traps more moisture.
So the question I have is, why not apply an immersion grade coating system at pipe supports, and for a short distance either side? This could transition back to a standard zinc epoxy system for the rest of the pipe. Isolation pads would be used at supports to prevent the coating from wearing off.
I'm interested to hear what coating specialists would say about this approach (economics, practicality), and if its been done before. I'm aware there are various other approaches such as I-rod, clockspring wrap etc.

 

[mk3223]

IMO, the non-metallic isolation pad may cause a maintenance issue if damaged. I saw the use of the metallic pad to protect the thin wall pipes in contact with support. I think there is not a perfect coating system to prevent it from damage, and it's a maintenance issue for the operation after years of service.

 

[brimmer]

Why not? No reason not to. Just make sure the coating you use is UV resistant, or put a topcoat over it (though not a bid deal as your corrosion control coating is still underneath). If you apply epoxy coatings over epoxy or some sort of paint, it is difficult to get them to adhere to each other, you will need to roughen the surface first. I prefer using some sort of composite wrap, it helps if there is an abrasion issue (between pipe & support). Its all what you make it, most don't as in projects coating is an afterthought, many just try for the easiest & cheapest, once turned over to operations its their problem.

 

[SJones]

An immersion grade coating will buy you some time, but the corrosion fundamentals of the arrangement won't change - it's all about the crevices.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.