Adhesion test and topcoating 1

[UtahWater]

What kindof adhesion numbers indicate a satisfactory candidate for top-coating? We have a steel tank with a 40 y.o. lead paint on the exterior that was topcoated 18 years ago with a Macropoxy 920 primer and Corothane II Urethane. The more recent topcoat is showing localized spots of lifting...we'd like to avoid (kick it down the road) the need to do a full removal of the lead coating. When doing glued-dolly tests, what range of numbers indicate an acceptable base coat? Thanks!

 

[CoCoE]

I hope your lead paint should be an epoxy.

Since you need to really ensure the sound coating, as a coating specialist I would suggest to get at least 6MPa as the acceptance criteria.

Regards

 

[Andrew1974]

Anything that exceeds 500 PSI on the ASTM D4541 test is what you want. That's a standard for most of the High Performance Epoxies on the market: SW Macropoxy 636, Devoe 235, Gulf Coast Paint's CM-15, Rustoleum 9100.