There are now many other metal primers on the market other than the old “shop primer” most steel fabrication and industrial facilities use. Don’t get me wrong, shop primer still has its place. For a product that you can buy for a very minimal price per gallon, you can get a minimal amount of protection needed for structural metal that will be covered up at some point.
Universal metal primers have certainly made a big splash. When looking for one, make sure you select a universal metal primer that can take a variety of topcoats. Many universal metal primers now are able to receive a variety of topcoats including alkyds, acrylics, urethane, silicone-alkyds, and epoxies. For large jobs, it is still possible to find a paint vendor that can supply a product such as this for a very reasonable price.
Fast dry epoxy primers have become popular selections to put under urethane and epoxy topcoats. These products dry quickly and are easy to spray, the only drawback here is that you most likely will need better surface preparation (SP6 commercial blast). You will also need to mix an “A” and “B” component and allow the appropriate “sweat in” time before spraying. Their costs are usually just slightly higher than the single-component universal metal primers.
“Wet on wet” metal primers have also been in the mix here recently. These are metal primers that can have a topcoat applied in as little as 20 minutes. They also can receive a variety of topcoats like urethane and epoxies. For a shop that is looking for premium production times, these types of products can certainly be the ticket. Amazingly, costs on these primers are very similar to the universal metal primers on the market.
Some potential pitfalls to avoid when selecting a metal primer are:
1) There are many grades of shop primers with all sorts of pricing. Make sure your shop primer contains around 50% in volume solids. This will help maintain good coverage and provide better overall quality. There are many 30% volume solids types of shop primers on the market that will increase your overall cost greatly because of their lack of coverage. In many cases you can purchase a better quality shop primer for the same price as a lower quality shop primer.
2) Some universal metal primers can only receive an acrylic or alkyd topcoat. While your project may only need an acrylic or alkyd topcoat, you can usually buy the premium version of universal metal primer for the same price. This will help later on down the line when someone in your shop might not remember what type of topcoat this primer can receive. By getting this right in the beginning, you will avoid potential problems later on down the road when you encounter a project that requires a more premium topcoat.
3) Fast dry epoxy primers can vary in dry times. Make sure you look at your dry times very closely as this product should dry in 30 minutes to the touch and you should be able to re-coat in two hours in ideal temperatures. Pricing on this product should also not be outrageous, as it is meant to be at a price point so you can build your paint mils at a reasonable price.
4) Keep in mind your level of surface preparation. SP2 and SP3 (hand tool & power tool clean) are usually sufficient for single-component primers. Although this form of surface preparation is also listed for epoxy primers as the minimum, it has been my experience that the mil scale on the steel needs to be removed. This will require a SP6 (commercial blast) surface preparation to adequately meet the needs of this type of product. Always remember, the coating you select will only perform to the level of surface preparation you complete.
There are other types of metal primers in addition to these, but these four classes of metal primers will cover the majority of your metal primer needs. For each project, try to balance your production times with the quality of primer needed for each application.