Acrylic or epoxy primer - which one to choose and why is more important than you think

Acrylic and epoxy primers are two different products with different chemistry, different properties and different purposes. They are not replacements - they are complements.

Acrylic primer is made on the basis of acrylic resin. After application, it creates a coating that fills irregularities well, is easy to sand and provides a good base for the topcoat. It is versatile and easy to use.

Epoxy primer is based on epoxy resin which, after hardening, creates a hard, tight and chemically resistant coating. Its main advantage is anti-corrosion protection - much better than in the case of acrylic primers. It creates a barrier impermeable to moisture, which means that even if air gets into the coating, without moisture there will be no oxidation of the metal.

Acrylic primers are the bread and butter of repair paint shops. They work well on polyester putties, smooth surfaces and old paint coatings prepared for renovation.

Acrylic primers are available in white, gray and black. The correct selection of the background color is not about aesthetics - it is a real saving of the base varnish and better matching of the final color.

For plastic elements - bumpers, mirrors, strips - an adhesion promoter is necessary before the acrylic primer. Without it, even the best primer will not have adequate adhesion to the plastic and will fall off the first time the element is bent.

Most acrylic primers can be used in three ways, depending on the amount of thinner added:

• Primer version - minimal amount of thinner, thicker consistency. Used as insulation for putty or old coating before applying filler.
• Bulking version - standard dilution. Fills minor scratches and irregularities, requires sanding before topcoating.
• Wet on wet version - maximum dilution. After several minutes of evaporation, you can apply the varnish without sanding - saving time on smaller repairs.

There are situations where an acrylic primer is simply not enough. Epoxy is not a more expensive alternative - it is a product for a different purpose.

• Direct to Metal - For any repair where bare metal is exposed, epoxy is the standard first coat. Acrylic on bare metal is a recipe for corrosion that will appear after several months or years.
• Under and above polyester putty - epoxy under the putty improves its adhesion to metal. The epoxy over the putty isolates it from subsequent layers and prevents discoloration from peroxides contained in the putty hardener.
• On sanded old coatings - epoxy as an insulating layer prevents the topcoat from marking the repair areas over time. This is one of the most common reasons for complaints about repairs that look good immediately after leaving the paint shop, but after a year they start to stand out.
• On aluminum - aluminum requires special protection against electrochemical corrosion. Epoxy is the right choice here.

It can be said that the foundation is good. It can also be proven.

MAVAR underlays undergo resistance tests in salt chambers in accordance with the ISO 9227 standard. The salt chamber simulates years of exposure to moisture and road salt within several dozen hours - our underlays emerge from it without any traces of corrosion.

We also conduct tropical tests - they simulate extreme conditions of high temperature and humidity typical of difficult climates. A coating that withstands tropical conditions will cope with the Polish winter and road salt without any problems.

These are not one-off tests when the product is introduced to the market. Each series of foundations goes through the same procedures - so that you can be sure that the product you open today works the same as the one we tested.

You can choose a cheaper foundation of unknown origin. But you won't know what's inside or how it will behave under the customer's paint in two years. We know - and we can prove it with technical documentation.

To keep things simple - rules that will suffice in 90% of repairs:

• Bare metal → always epoxy as the first layer. Never apply acrylic directly to metal if you want the repair to last.
• Polyester putty → epoxy under and above the putty. Putty insulation is insurance against discoloration and adhesion problems.
• Leveling and filling → acrylic filler. On a well-insulated surface, the acrylic filler will do its job best.
• Plastics → adhesion promoter over everything else. Without it, no primer will guarantee durability on plastic.

Use products from the same manufacturer throughout the entire system - the primer, base coat and clear coat should come from one product family. Mixing systems from different manufacturers is the most common cause of compatibility problems that cannot be predicted without testing.

And always check the product's technical data sheet before application. It is the ultimate source of information on mixing ratios, evaporation times and compatibility. The technical data sheet is an agreement between the manufacturer and the painter - if you follow it, the manufacturer is responsible for the result.