Primer And Hot Rods - Scuff &Squirt

Beauty is in the eye of the beholder. That's a statement that holds true in the street rod/hot rod hobby as well as it does in scores of other situations. Some folks wouldn't feel comfortable driving a primered car; for others it's just the opposite. For me, the sight of an early car or truck in primer (or even a suede primer-like finish, for that matter) immediately says "hot rod" while a shiny, painted car or truck of the same year, make, or model instantly registers as a "street rod." This may not be a universally accurate impression, but that's just how my mind works in this regard.

This perception harkens back to my young, impressionable days in the late '60s when I was first exposed to the local hot rods that consumed me. Back then, as I guess is at least partially true today as well, dollars were the factor. A good professional paint job wasn't (and isn't) cheap. Many would rather spend that hard-earned cash on hard parts and gas for cruisin' than shiny paint and lots of chromed parts. Just keep in mind that primer is not intended or formulated to be a topcoat. It will not seal the surface as effectively or protect itself from UV light as paint does, so it'll never stand up as well or last as long as an actual finish paint.

That said, the prep work for a rod that's destined to sport primer as its final finish is just as important as that required for a good-looking, long-lasting "real" paint job-and above and beyond that, choosing the correct materials is also important. So, with this in mind, I'd like to share how I've been handling the situation for many years. Keep in mind that I'm way behind the curve when it comes to all the new politically/environmentally correct products and methods espoused these days (though I am looking forward to getting an education in current products and methods in the near future).

Prep Is The Key
It doesn't matter what your goal is finish-wise; if your prep work sucks, so will your paint job. Spraying whatever over a rough, dirty, or rusted subject is a waste of time, energy, and material-adhesion and non-contamination is the goal for any finish.

Here are a couple examples. Say you're getting around to prepping that old steel Model A body you snagged from the local swap meet. The first thing you're gonna want to do is wash it. Yep, grab the bucket and car wash soap and get to work. This initial step will rid the body of most loose grit and grime and ready it for the next step. This is the starting point for that new aftermarket 'glass body as well. Once the body is clean and dry, the next step would be a good wipe-down with a dedicated wax and grease remover, or some Naptha (a wetted clean rag) followed by a dry, clean rag will do the trick. This step will rid the surface of any foreign contaminants like oils, silicones, or in the case of a new fiberglass body or component, mold release agent (the coating used to keep a fiberglass piece from sticking in its mold). You never, with either steel or fiberglass, hit it with sandpaper before a proper cleaning; if you do, you have a really good chance of forcing any contaminants into the surface, causing headaches during or shortly after the finish application-or the application of body filler as well. Good adhesion requires a clean and correctly prepared surface. This holds true for body filler as well as primer and/or paint.

With the surface clean and dry, the next step would be to either mechanically or chemically roughen the surface. This aids in a mechanical bond of any coating or filler by providing a surface that is rough enough to let the coating, again either body filler or primer, to grab on to the surface. This step, in the case of a metal surface anyway, can be achieved using a metal prep solution that chemically etches the surface. Or, in the case of either metal or fiberglass, light sanding will mechanically "groove" the surface, aiding in adhesion.

With the surface cleaned and prepped, the next step would be whatever bodywork or repairs (a good subject for a future discussion) may be required prior to application of body filler or a prime coat. As an aside, if any of your bodywork involved welding or patching of sheetmetal, keep in mind that the new panel should be prepped as the original was. Also, for those of you who use a flux-core wire in your wire-feed welders, you'll have to thoroughly clean the welds before grinding to remove any contaminants that may adversely affect both body filler and/or primer-a lesson I learned the hard way years ago.

Choose Your Weapon(S)
Primer selection is important, especially if you're like me and your primer will sometimes be considered your finish coat. There are a lot of different types of automotive primers available these days, depending on where you're located in the country. Some states are much more stringent in the control of product availability and use than others, so some options are off the table. The main types are polyester primers, lacquer primers, epoxy primers, urethane primers, and self-etching primers. Some are sealer primers and some are filler primers, as well.

Sealer Primer
For the record, a sealer primer does just what its name implies: It seals the surface as well as primes. The sealer component acts as a barrier between the substrate and the topcoat. Some folks recommend finishing a standard primer job with a coat of sealer. Sealers alone aren't necessarily required, though, as many surfacers do double-duty as a sealer and surfacer. But it's a possible insurance policy to help prevent things from going wrong, like solvents from a topcoat rewetting and possibly harming a basecoat, or allowing the colored hardener in body filler to bleed through a finish coat.

Filler Primer
Filler primers are high-solid primers that go on thick and fill minor imperfections or build up a surface to help flatten it out.

Primer Surfacer
Primer surfacers are also a high-solids type of primer that's not quite as thick as a true filler primer but does offer a moderate amount of filling properties.

Polyester Primer
Polyester primer is a corrosion-resistant sanding primer based on an air-drying polyester resin (akin to fiberglass resin). It is fast drying and has excellent filling properties and adhesion over fiberglass, metal, plastic, and wood. It can be topcoated with all types of finishes, acrylics, lacquers, synthetic enamels, and two-component urethane coatings.

Lacquer Primer
Quick-Dry Primer Surfacer is a single-component lacquer primer. Premium lacquer primer offers high-build and adhesion properties and many are also corrosion-resistant, and may be wet- or dry-sanded. Lacquer primer can be used as a base for acrylic enamels, synthetic enamels, and acrylic lacquer finishes.

Epoxy Primer
Epoxy primer is an excellent corrosion-resistant primer that offers good adhesion on many types of properly prepared metal, aluminum, fiberglass, and body filler materials. Epoxy primer is a two-part primer that's often pretty tough to sand but can be topcoated with many current basecoats. It can be used as a sealer and applied wet-on-wet as well.

Urethane Primer
Urethane primer is a high-performance, high-build, two-component primer surfacer that is oftentimes chromate free. When it's applied over properly prepared steel, galvanized steel, aluminum, and/or fiberglass, two-part urethane primer provides excellent adhesion, some corrosion resistance, and superior hiding qualities. Urethane primer provides many advantages of epoxy primer but sands easier and is less dense. It can also be topcoated with all modern basecoats.

Self-Etching Primer
Self-etching (also known as DTM or direct to metal) primers use an acid-based catalyst, which actually bites into the metal and helps neutralize microscopic corrosion in the process. Note: Get professional input with regards to the use of self-etching products, as they are NOT compatible with many other primers, fillers, and topcoats. As a rule of thumb, I never use a self-etching primer over a polyester primer, polyester body filler, or fiberglass. Also, I never use a polyester primer or body filler over self-etching primer. As I said, check the primer manufacturer's recommendations for use and incompatibilities for any other type of two-part catalyzed primer.

Application
Since there are lots of various substrates available these days (both brand-wise and composition-wise), it's impossible to cover every suggested application regimen here, but read the instructions as a rule of thumb! When it comes to priming and painting, reading the instructions after, or halfway through, the job just isn't gonna cut it.