Q. I am a manufacturing engineer working on a project for an oil- and gas-producing energy company. We have to fabricate and paint some fire protection water storage tanks. The specifications call for mill galvanized, not hot dip galvanized steel as the construction material.
The client’s data sheet requires internal and external painting after an abrasive blast surface preparation. Therefore, I don’t see any advantage to using mill galvanized steel, since it needs to be removed by abrasion blast later on. Or maybe, based on your expertise, you can recommend a paint system that can have perfect adhesion to the mill galvanized steel? And do you have any idea as to the purpose of using mill galvanized steel at all? W.R.
A. I’ll answer your last question first. The purpose for using mill galvanized steel in the fabrication of your client’s tanks is to prevent corrosion in shipment to and in your plant during storage and fabrication.
Yes, there are finish systems that will adhere to mill galvanized steel—however, if you use one you will not be in compliance with your client’s specifications and he will probably reject the tanks.
If your client called out a paint system in his specifications, I recommend you use it. If not, typical coating for water tanks include zinc rich primers topcoated using coal tar epoxy, chlorinate rubber or vinyl enamels. I don’t recommend specific paint suppliers in this column. For specific finish systems, I suggest you contact SSPC (The Society for Protective Coatings), their website is sspc.org.