×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

pinholes in epoxy coating

pinholes in epoxy coating

pinholes in epoxy coating

(OP)
I remember reading that pinholes in the epoxy coating is all it takes to seriously corrode the underlying material and that the epoxy coating is basically useless when the coating is scratched up.

I'm thinking this might be true for galvanic corrosion between two dissimilar metals in contact. But what about in submerged applications? Will a small pinhole in the coating of a submerged steel plate be the cause of a serious corrosion failure? I thought it was the wetted area that matters.

RE: pinholes in epoxy coating

If most of the surface area is protected with a coating, the corrosion will be intensified in an area with pinholes. The pinhole area is the anode in a galvanic reaction.

RE: pinholes in epoxy coating

Do you have a cathodic protection system protecting the plate?  It's important to fix as many pinholes as you can, but you should have a cathodic protection system and coating working together for the best protection.

The presence of a pinhole in an FBE coating will not necessarily cause a corrosion failure.  There are thousands of miles of pipeline with FBE coating, and even though pinholes are fixed prior to backfilling not every single one gets fixed.  

   

RE: pinholes in epoxy coating

(OP)
How well will an epoxy coated steel pipe work in a tank containing potable water?

RE: pinholes in epoxy coating

For potable water tanks, they put two or three coats of epoxy on, which will really reduce the likelihood of pinholes.  After that, they holiday test the coating and repair any flaws. After the tank is put into service for 11 months, the tank is drained, inspected and any rust spots are repaired.
A pipe in a potable water tank should have all the same requirements. Pinholes are not acceptable.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources