by Ron Joseph
Paints for Salt Water Protection
Q: What over the counter primer and protection is recommended to prevent or retard corrosion and / or rusting of mild steel exposed to saltwater vapor and occasional saltwater contact? Your comments and suggestions are sincerely appreciated.
A: It all starts with the surface preparation of at the mild steel. Ideally, you should abrasive blast the steel to a near-white finish. I assume that since you are looking for over-the-counter paints you are probably doing a home project. In that case, you probably don't have the resources to abrasive blast the steel. The next best option, but by far not the ideal is to abrade the surface to a clean finish and ensure that you remove all rust and corrosion products.
Since you are looking for over-the-counter primers, I suggest that you ask a technical person at your local paint store for a corrosion resistant primer that is intended for the protection of steel. The most effective primers are based on a zinc chromate, but since many states now regulate the use off this pigment you might need to settle for something less. If I had to a choice I would prefer using a two-component epoxy primer to any single component product that is available at a local paint store. Again, you may simply need to make do with what ever primer you can get.
Finally, you will want to apply to coats of the marine spar varnish or something similar to protect the steel from the ingress of moisture vapor. Ideally, you would apply a two-component polyurethane or an epoxy siloxane, but these coatings are only available from specialty paint stores, and it is possible that you don't have access to such a store in your local area.
If you are able to locate an industrial paint store that stocks high-performance epoxies and polyurethanes, the technical salesperson should be able to select the appropriate coatings for you.