Chemical Treatment AND Coating for Corrosion Protection

1. No (Aramco standards are not international)

2.
If changing the material is not an option, and coatings are not considered effective (for the design life), there is nothing left, (CP being totally weird) in the corrosion control sphere, other than to modify the fluid and load a big corrosion allowance if pitting isn't envisaged. That fluid modification could be a process treatment, or it could be a chemical treatment. I almost neglected the last option: prayer.

Steve Jones
Corrosion Management Consultant


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

I don't know any paint manufacturer that wants an intermediate coating between the metal and their paint. A failure of the intermediate layer would compromise their product.

@Tug the coating goes onto the steel, the chemical goes into the fluid.

Steve Jones
Corrosion Management Consultant


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

I have seen inhibitors used to treat the process fluid(s). It does help - but the crux is maintenance of the system. You will need to develop a routine testing program for it. The operator is going to have add inhibitor and make sure that the "blend is correct". In the services that I have dealt with this, the inner wall of the pipe has been left bare - but it may not be as aggressive of an environment as you're referring to. I would tend to think that coating the inner wall may be a two edged sword - as if there is no "background protection" such as CP then the coating defects are going to corrode rapidly, as they will be anodic compared to the surrounding areas. In theory, if the proper inhibitor were applied and maintenance was done correctly, then you could dramatically reduce the corrosion cell. Some corrosion would still be present. Increase the wall thickness as stated by others. The issue with what you are describing - are the details, need to get the right inhibitor with the right coating. And then the inhibitor blend would need routine testing and monitoring.

Ah, I didn't get that the corrosion is on the process side. Corrosion inhibitors (including oxygen scavengers) in my experience all generate a very caustic environment which is hard on coatings, especially at elevated temperatures. Coatings that can tolerate pH above 10 at operating temperatures should work well.

Galvanic or impressed current systems could work well. Protecting pipe is difficult due to the length, too many anodes. Y'all got me thinking. I have an idea for impressed current protection of piping...

@Tug - you are too late. Already done. Google 'RCP cathodic protection' although it is only for stainless piping, admittedly

Steve Jones
Corrosion Management Consultant


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

I'm thinking a string of cathodes that can be blown in to existing small bore piping and can penetrate at flange gaskets. No hot work!

I have seen coatings with anodes "baked in". Normally zinc. Would have to figure out the specifics here - but I don't see why something like that would not work.

alchemon said:

I have seen coatings with anodes "baked in". Normally zinc. Would have to figure out the specifics here - but I don't see why something like that would not work.

Click to expand...

Welding will be a real challenge.

I thought your original post said that the inhibitor was for the welds and holidays (ie I read as no coating here)

@alchemon, thanks for your replies.

Using corrosion inhibitor with coating is mandated by the client, but I wanted to:
1) understand the logic behind such requirement (I was guessing when I mentioned that the inhibitor will work on welds and holidays as the CP does).
2) explore other options as I know that it will not work as expected because managing the inhibitor system is very challenging (the service is very corrosive).

1. The logic is: somebody wants to spend a lot of money in an attempt to get a warm, fuzzy feeling in the best of both options (if it is the same company that I alluded to above, I've been through it with them a couple of times). I thought that the principal protagonists had all retired by now. Must be a lasting legacy.

Steve Jones
Corrosion Management Consultant


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