There are two main types of primer; self-etching and regular primer. What’s the difference between both types?
Regular primer is an undercoat with no special additives or chemicals. It is traditionally a white, grey, or dark undercoat designed to improve paint adhesion, bonding, and smoothness. It is primarily used in wood, plaster, and masonry.
On the other hand, the self-etching primer has chemicals included in its formula. These chemicals have a high acidic presence that helps the undercoat etch or corrode the material. The etching helps to produce a textured coating the paint or top coat to stick on.
Self-etching primers are designed for slick surfaces, such as metal, fiberglass, and aluminum, that paints can’t stick to. So, the undercoat will abrade the material slightly to allow the paint to adhere properly
Regular primer is a type of undercoat that is designed with adhesive compounds and binders. It is used as an undercoat before laying the paint or topcoat. When dry, it produces an even and slightly textured finish that help the paint to stick. Its even finish makes the topcoat appear smooth and even when dry.
Regular primer is usually white or grey. However, there are now other colors available. The broad range of colors is made possible because the undercoat is common on surfaces that require decor and detail work.
Most regular primers are gotten from synthetic resins, solvents (usually water), and additives. Its simple formula makes it ideal for most surfaces. It also makes it a suitable undercoat for any type of paint without repelling it.
Regular primer comes in both water-based and oil-based versions. The water-based version is used for water-based paints including latex, acrylic, and chalk. The Oil-based version (type) is ideal for oil-based paints.
However, regular primers have one flaw — it doesn’t work well on slick and metal surfaces.
When Should You Use it?
You should use regular primer when you want to paint over a porous surface, such as wood or clay (brick). You should also use it when you want to paint over drywall, concrete, masonry, plastic, and the likes. Usually, any surface material except metal and fiberglass should be coated with regular primer before painting.
If you are working on a defective surface or if the surface is riddled with dirt, grease, or oils, you should use a stain-blocking regular primer like shellac to seal the surface.
Also, when you are working with any type of paint apart from automotive or metal paints, you should use it.
Self-etching primer is an undercoat that etches or corrodes the surface to allow the topcoat to stick properly. It is designed for slick materials including metal, aluminum, fiberglass, and steel.
Paints usually have a hard time sticking to these materials since the surface is non-porous and smooth. This was why self-etching primers were designed. When applied it corrodes the material to produce a textured surface that the paint can bite into.
It usually comes in a spray can which is an irony since its coating is usually thick. The best part of self-etching primers is that you only need one coat of it.
It is also used for automotive paints and metal paints like rust-oleum paint. However, it has a flaw — painting over it is harder.
When Should You Use It?
You should use self-etching primer when you want to paint over a metal surface or if you want to prevent rust. Metal surfaces including aluminum, steel, and even fiberglass should all be coated with self-etching primer before being painted over.
You should also use it when working with automotive paint. Paints designed for metal, cars, and steel all require a coat of self-etching primer.
Regular vs Self-Etching Primer
To compare both types of base coats, we’ll use the same feature and see which one is better:
Regular primer is gotten from a combination of solvents, binders, and synthetic resins. Its formula is simple and doesn’t have any special chemicals or acids in its formula. The key ingredient is the binder — this is what gives it adhesion and good binding.
On the other hand, the Self-etching primer has a more complex formula. It is designed with chemicals and acids, and its main ingredient is a phosphoric acid ester. The acid is responsible for etching materials to allow the topcoat to stick.
The Dry Time
Regular primer dries faster than self-etching primer. On average it dried within 2 hours (depending on the type). On the other hand, Self-etching primer takes between 3-5 hours to dry. It has a long dry time because of the complex formula.
Regular primer costs more than self-etching primer per unit. On average, a gallon of regular primer will cost you about $20 while a 16-ounce spray can of self-etching primer costs about $7. However, regular primers come in paint cans which means you get more of it.
So for instance, if you were to cover a 225-square-foot surface, a gallon of regular primer at $22 will be enough while for the self-etching primer, you’ll need about 8 16-ounce spray cans at $7 each ($56). So, in the long run, regular primer is cheaper.
Regular primers are ideal for porous surfaces, such as wood and brick. You can also use them on masonry, concrete, plaster, drywall, and the like.
Self-etching primer is ideal for metal surfaces. You can’t use it on porous surfaces, such as wood, because the it is designed to etch or corrode material and wood doesn’t need corrosion.
Regular primer can also be used on metal. Though it won’t work great on metal and aluminum, it will still produce a result that will be smooth and durable for a while.
The Ideal Type of Paint
Regular primers are universal and can work with virtually any type of paint. Water-based, oil-based, and metal paints can all be used over it, though the level of smoothness may vary.
You can only use automotive and metal paints over self-etching primer. This gives you a limited range of choices.
Self-etching primers are easier to apply than regular primers because they come in a spray can. Also, you just need one coat of it.
On the other hand, regular primers come in a can, so you’ll need a paintbrush to apply it, which will take more time and can reveal brush marks. You can also use a spray gun but this will require a few minutes of prep work (to thin it). You also need at least 2 coats of regular primer for proper surface coverage.
However, after applying the self-etching primer, you must dry or wet sand it before painting over it. In some cases, you also need to apply an additional coat of epoxy primer.
Regular primers can’t prevent rust unless sealed with a rust-resistant sealant or top coat. Self-etching primer can prevent rust on metal surfaces. This is because they bind to the metal and produce a moisture-resistant coating.
Regular primer is a better sealant than a self-etching primer. That’s because they are designed to seal and block stains, moisture, and oils from bleeding through the paint when applied.
Self-etching primer is not a great sealant. It is more tuned to stop moisture from penetrating the metal underneath. It’s not ideal for sealing stains and moisture but it’s great for protecting the material underneath from spills.
In simple words, regular primer prevents moisture and oils from coming up from the surface. Self-etching primer prevents moisture and oils from penetrating or going down to the material underneath.
Related Read: Water Based Primer vs Oil Based Primer?
In summary, both primers are great undercoats, but they have different purposes.
Regular primer is designed to seal imperfections on porous surfaces and create a textured layer for paint to stick to. While self-etching primer is designed to stick to slick or non-porous surfaces and help the paint to stick over them too.
Tony is a professional painter and an author of DIY Geeks. Tony has completed over 1,000 painting projects for his clients. It's safe to say he knows what he Is talking about,