Improvised Cathodic Protection

[serendepidy]

We have had a failure on our plant. In order to restart we have had to replace an elbow in a 150 NB CL 150 epoxy piping run, with a SS316 elbow with carbon steels flanges. The pipeline holds relatively stagnant seawater in a vacuum line.

I would like to improvise a cathodic protection system for the carbon steel flanges ? Can anyone suggest a way I might be able to do this ? Could it be as simple as wrapping the bolts in wire, snd apply a voltage and current and if so can anyway suggest how best to do this ?

 

[EdStainless]

Maybe too late, but you should have coated the inside of the 316. That would have helped a lot.
You need an anode for CP. What will be the anode in your system?

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Plymouth Tube

 

[SJones]

Surely, the repair can only be classed as temporary? At some time, sooner rather than later, that elbow will have to come out. Problem is, you are too late to do anything to the materials. If you have a spare access fitting close by, you may be able to get an RCP (resistor controlled cathodic protection device)to do some work (but seeing as how a 'lash up' repair was entered into this may be too advanced a solution!). The principal issue is that you now have a stainless/bare carbon steel/coated carbon steel arrangement which does not bode well for the carbon steel flange material in stagnant seawater. The only recourse would appear to be appropriate chemical treatment of the water.

Steve Jones
Materials & Corrosion Engineer

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