Surface rust is appearing after only a few days using a water based paint

We are a manufacturer of steel products used in the asphalt paving industry. We have made a change to our dip painting operation. We were using a solvent based bituminous paint and are now using a water based bituminous paint. We never had rusting problems with our steel product using the solvent based paint for up to a year when exposed to weather. We now have a surface rust problem after only a few days when exposed to weather. The steel is heated to approx. 85 degrees before being dipped. The solid content is around 60% The steel does have oil residue in varying degrees. Any suggestions?

Hi William,

I think the answer to your problem is kind of obvious. Your new water-based paint is not as corrosion-resistant as the old solvent-based material.

You should either go back to the old paint, find a new water-based paint with better corrosion resistance properties, or improve the chemical pretreatment of your parts prior to painting.