Determining active corrosion on buried pipeline

[Willydan]

In that there are numerous deposits that can be found when a buried pipeline is exposed, is there a simple test to determine if the deposit represents active corrosion?

 

[Metalguy]

Can't you just scrape the deposits off and see what's underneath?

 

[Willydan]

Sure but if I find corrosion how do I know it is active? I know that there are chemical tests for MIC, etc. but what about ordinary corrosion?

 

[Metalguy]

A variety of corrosion-monitoring probes/devices exist commercially. A simple visual exam of a surface should reveal any metal loss--assuming you can expose the surface. Sounds like you are looking for an in-place monitoring system so you don't have to dig up the pipe.

A good rule of thumb is to assume you DO have active corrosion unless some measure(s) are taken to prevent it, or the environment is benign. Assuming again that your pipe is steel/cast iron, remember that it generally wants to return to its natural form, iron oxide.

 

[Willydan]

We typically expose buried steel pipelines and discover various deposits and we need to be able to tell if the area in question is currently "active". I've heard that pH of the electrolite may be an indicator, I've also heard that if the exposed metal under the deposit is new looking that this is also an indicator. I wanted to know if there was any absolute way of indicating that the area is active at the time it is exposed.

 

[rorschach]

Is CP being used? wouldn't a CP current survey show you where the potential for corrosion exists?