We all love epoxy primer for its excellent work filling cracks and decks. Now, you are wondering whether you can get the same bonding quality when you use the primer over etch primer.
You are probably confused for two reasons. First, you know that epoxy primer is best applied on a clean dry surface. Is a surface with etch primer good enough for the epoxy to adhere?
The other reason for your doubt is the widespread belief that etch primers contain residual acid which it difficult for the epoxy to cure properly.
This article will cover all your concerns. Whether it is about epoxy over etch primer making the bare metal feel dryer or the epoxy not adhering.
Understanding Epoxy and Etch Primers
Etch primers are excellent for priming bare metal surfaces that need to be ready in no time. You only need to apply a thin coat for the metal to etch and have a strong bond. Because they dry fast, you can apply the topcoat a little while after using the etch primer.
The mix of phosphoric acid and zinc means etch primers can only provide a surface coating or reduce the effects of rust.
Epoxy primers offer great adhesion and protect various types of metal from corrosion. These primers are excellent sealers that prevent surfaces from getting contaminated. The bonding ability of epoxy primers makes them great for filling cracks and dents. Unlike etch primers which you can make allowances for as regards sanding, epoxy is often a non-sanding primer.
It’s clearer now that you can use both primers on bare metal to protect the surface from corrosion. Do these similarities mean that the two primers can go over each other?
Can You Put Epoxy Primer Over Etch Primer?
The simple answer is YES, you can. You can apply epoxy primer over etch primer to create a level surface. For the epoxy to work well, you need to take some steps, one of which is making sure the surface is clean and dry.
The brand of epoxy you have can also determine whether or not you can have the etch primer underneath. Some brands work well with self-etching primers while others may not be suitable for the task. You will need to test these kinds to see if they can perform well.
If the product manufacturers recommend not using epoxy over the etching primer, it is best to stick to that.
Suitable epoxy brands that can go over etch primers will often indicate this in this product information. These manufacturers often recommend taking extra steps before applying epoxy. Sanding the etch primer before putting the epoxy is a necessary step that helps the primer adhere properly.
When in doubt, performing a test is a smart idea. Get a spare material and apply the etch primer. Leave it to dry for a while before applying the epoxy primer and see if you get good results. If you cannot get an old material to perform the patch test, find a hidden area on the original material and test both primers.
Do Etch Primers Require Sanding Before Applying Epoxy?
Working on a clean and dry surface is important so that the etch primer adheres correctly.
Some manufacturers do not recommend directly sanding etch primers because the product has an acidic base. They rather advise that you apply the coat of epoxy primer over the etch and then sand that if needed. Whether you stick to these kinds or purchase primers you can sand over, always remember to wear your respirator when applying or sanding etch primer.
The most important factor that determines whether or not you sand the self-etching primer is the particular product you have. With some primers, you can apply another paint or primer without scraping. Other types may need manual scuffing after the base coat dries.
Pay attention to the instructions that come with the product to know if sanding is necessary. Primers usually do not require sanding so if the product specifically states not to sand, go ahead and apply the epoxy.
Sanding the coated surface is essential if the manufacturer clearly states this and skipping this step may affect results. If there are no instructions at all, you will have to decide between testing a part or applying the epoxy primer on the freshly coated surface.
If you choose to sand the surface, here are some sanding tips to remember:
- Allow the etch primer to dry for 3 hours or more before dry sanding
- If you are wet sanding, 30 minutes or less is enough drying time
- Use 220-grit sandpaper for best results
- Maintain a 90° angle while sanding the whole surface
- Sand at a slow rate as sanding too fast can make the surface rough
When Should You Use Epoxy primer Over Etch Primer?
Epoxy primer offers many advantages as a top-quality sealer. Is applying the primer over an etch primer suitable in all situations? Here are some conditions in which epoxy will be best for:
Over Clean Metal
You are probably used to seeing epoxy used over fabricated metal parts but the primer is just as good for stripped surfaces. This is where the importance of sanding the etch primer is most evident.
Epoxy primer is excellent for sealing bare metal to prevent corrosion. It does this by sealing out the oxygen in the metal.
Etch primer is great for reducing the effects of rust but it does not inhibit corrosion like epoxy. Put the epoxy over the etch to cancel the chances of moisture penetrating.
On Combined Surfaces
Because of its excellent adhesion properties, epoxy will stick to painted, filled, or primed surfaces. Most coatings can only be efficient when the surface is uniform but epoxy differs here.
You will need to blend the surface first if it needs filling since epoxy has a minimal build quality. Etch primers are excellent fillers so you are making the right decision by applying the epoxy over it.
For Stacking
So long as the etch primer has a good surface texture, the epoxy primer will adhere. If part of the etch-primed surface needs to be corrected, then epoxy will be a good fit. It can provide light filling for stacking.
Not many primers are great for this but the mechanical hold that epoxy provides makes it perfect for stacking coatings. After filling the dent or crack with the etch primer, you can apply as much epoxy primer as you require.
Long-term Maintenance
Using epoxy over etch primer is a brilliant idea if you need to protect a project long-term before painting. Sometimes, the metal has to sit in for a while and the temperature in the storage area can cause corrosion within a short while.
With the primer’s sealing qualities, you can come back to the project when you are ready and not have to deal with a rusted surface.
Final Sealing
Applying epoxy as a final sealer before the base coat works just fine. If you have concerns about the paint peeling, putting the epoxy primer over the etch is just right. You can trust the bonding qualities of epoxy to prevent flaking.
When using epoxy as a final sealer, avoid applying too many coats to keep the surface smooth enough for your base coat.
Tips for Correctly Applying Epoxy Over Etch Primer
It is not enough to be aware of the situations when applying epoxy over etch is recommended. Pay attention to the following practices to ensure your base coat and topcoat come out great.
- Block the areas that will not be primed with tape to protect them from overspray.
- Use a rougher sandpaper grit to remove any existing corrosion on the surface.
- Mix the epoxy properly to reduce film buildup.
- Use a spray gun that can spread the primer evenly to reduce cleaning time.
- If you wait for days for the primer to dry, sand the surface lightly before applying the last coat of epoxy.
- Ensure you are wearing the necessary safety equipment while applying the epoxy.
Conclusion
Putting epoxy primer over etch primer is great for building up a leveled surface. Remember to begin work on a dry clean surface. Mixing the parts of the epoxy properly is important for good bonding. The topcoat will adhere well if you spend enough time mixing the primer correctly.
Always review the manufacturer’s information regarding applying epoxy over etch primer. If the particular product advises against using epoxy over etch primers, get an alternative product for your project.
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