Ask the Expert Question-and-Answer Archive

by Ron Joseph

Paint Compatibility

Q. In a new wastewater treatment tank we painted over ductile iron pipe that had a bituminous coating. We used an epoxy based paint and the epoxy paint pealed off lifting the bituminous material with it. Are there compatibility issues? Should we have removed the bituminous coating or should we haveused a special primer? Thank you for your assistance.

A. In all likelihood the original bituminous paint was thinned with lacquer thinners or perhaps even mineral spirits. The epoxy paint probably contained stronger solvents and acted like a paint remover when it was applied over the old paint.

Therefore, to answer your question; yes, the bituminous paint should probably have been totally removed back to the bare metal.

Regards,

Ron Joseph