Self-etching primers are one of the best primers to use on metal or fiberglass painting projects. Painting on metal or fiberglass is hard, as the surfaces are smooth. Self-etching primer makes the process easier by creating a rougher surface so that the paint can stick. They are also used on bare metals as they create a strong barrier for moisture, thus protecting the metal from rusting.
But about painting over self-etching primer, it’s better not to paint straight over etch primer. In most cases, self-etching primers come with acidic contents that may lead to the acids leaching into your topcoat. However, there are specially formulated self-etching primers that are okay to be directly painted. So, read the manufacturer‘s instructions and be sure about it.
Self-etching primers are typically made out of an acid and zinc formula. The acid is what burns or etches the metal surface and embeds the zinc into it, which then protects it from rust. The etching action helps the primers “bite” into the metal and create a stronger bond.
There is more information that you need to know about painting over self-etching primer, and we’ve put all of it together in this article. Let’s get started!
Can You Paint Directly Over Self-Etching Primer?
Sanding and applying another layer of primer before you paint self-etching primer is a better decision instead of painting directly over the primer. Still, whether or not you can paint straight over self-etching primer depends on the particular product you are using.
Without another layer of primer over self-etching primers, chances are the paint won’t adhere.
Some manufacturers instruct using another primer on top of them first before painting, while others do not require such things. So check your manufacturer’s manual to find the exact answer.
Not all self-etching primers offer the same protection to the underlying surface they’re applied to. Reading the product information will also help you in this aspect. You will know if the primer is offering the type of protection you are particularly looking for.
Regardless of whether or not there is a need for another primer to be applied over the self-etching primer, always make sure the underlying surface is thoroughly dried and cured before applying the paint. Otherwise, you will end up with a poor finish and run the risk of damaging the underlying surface.
How Long After Self Etch Primer Can I Paint Over?
Self-etching primers take longer to dry completely than regular primers. On average, self-etching primers need 5 hours whereas regular primers are ready to be painted within 2 hours. The time difference is because both primers are formulated differently.
Moreover, the duration depends on the surface you’re priming over, the temperature and humidity of your living area, and things like these.
In general, the self-etching primer dries to the touch within 30 minutes. But still, you should wait a bit more to set it better. And, if the temperature is below 70°F (or 21.1°C), you should allow for more drying time because the chemical reaction requires heat to thicken. Furthermore, the recommended humidity level is 50%.
The less humid the air is, the faster a self-etching primer will dry. Check the manufacturer’s recommendation in your product manual for more specific information.
Metal surfaces can be a bit of a pain to deal with because you have to get everything right or the paint job won’t look as good as you imagined. You should sand the metal panel first to remove any irregularities from the surface using fine grit sandpaper and later clean it with a rag wet with mineral spirit.
This will ensure a smooth finish after you spray on the self-etching primer. Maintain an appropriate distance from the surface when applying the primer, generally anywhere from 6-12 inches, depending on your preference, as long as it’s not too close. Apply two or three thin coats with two minutes of drying in between them.
Do not paint over it too soon, or else the finish will look uneven and have bubbles or streaks. It may also result in the paint peeling or scratching off easily.
What Primer to Use Over Self-Etching Primer?
Urethane primers work well over self etch primer if you decide to paint over with another primer. Urethane serves as an effective sealer, preventing any acids from self etch primer from seeping into your topcoat, which is a common problems with painting over self-etch primers. Once a urethane primer has been applied, the self etch primer can be top coated with just about anything.
Do not use epoxy over self-etching primers. Any residual acid from the etch primer can harm the curing of the epoxy, leading to longer drying times, and possible blistering. As a result, your top coating will have problems adhering to the substrate.
And, if you ask ‘what type of paint is suitable for going over self-etching primer?’
Not all types of paint will go smoothly on self-etching primer and adhere well, sadly. Paints that are specially formulated to use on steel, cars, metal, or aluminum are the best options for self-etching primer. So, yes, the option is quite limited compared to regular primer.
Does Self-Etching Primer Need to be Sanded?
Depending on the specific product, self-etching primer may or may not require sanding. Some self-etching primers do not need manual scuffing, allowing you to continue working with another primer or paint when it dries. Some people may only require a light scuff.
In general, you should read any accompanying instructions to determine whether sanding is required. Manufacturers sometimes clearly mention that sanding is not necessary. You should avoid sanding in this case because self-etch primer is primarily designed that way. However, some manufacturers do advise sanding the freshly coated surface after the primer has dried. In such a case, you should consider sanding as an important step for better primer or paint adhesion.