Cement Truck Finish

Q. We manufacture cement trucks. These are both the rotating drum type for general use and the open-top tub type used at highway construction sites. The mixers and tubs are made from 14-gage hot rolled steel. The paint must be resistant to abrasion by the aggregate in the mix, and to corrosion from the alkali in the cement and the acid in the wash water used for cleanup. We do our painting out in the manufacturing shop floor, although we plan to add a paint line to our shop. However, we are having paint problems. These problems run from primer and paint peeling to severe rusting. Before we order any painting and metal preparation equipment, we need to know the materials to use and procedures to follow to improve our paint finish. T. L.

A. As I’ve stated many times, the key to a successful paint finish system is proper surface preparation. Surface preparation methods for hot rolled steel include abrasive blasting, pickling and phosphatizing. In any event, mill scale, rust, oil and soils must be removed before painting to ensure adhesion. Since you have a relatively small shop, I suggest you abrasive blast the hot rolled steel surface to “white metal” and apply a primer immediately.

Since a cement truck’s paint undergoes exposure to acids, alkalis and severe abrasion, it requires a high--quality chemical- and abrasion-resistant finish system. The most serviceable finish system for this application already has wide acceptance in the transportation and chemical industries. I recommend you coat all “white metal” abrasive-blasted surfaces with a two-component epoxy primer and top coat that with a two-component polyurethane or acrylic urethane enamel. The resultant finish system will provide state-of-the-art durability for your cement trucks.