Self-Etching Primer
The key to getting paint to stick to bare metal is all in the metal prep and using the right primers. Self-etching primer contains a mild acid that actually etches the bare metal to create a superior bond between the primer and the metal. Once the area is coated in self-etching primer, more traditional primers can be used to build out the surface.
10 Responses to “Self-Etching Primer”
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Hi Mark. I look forward to your videos every week and always seem to learn something new. My question: If I apply a zinc phosphate coating on my bare metal (such as After Blast by Eastwood), can I still use a self-etching primer over top of it? Thanks.
Hi Gabriel,
Thank you for your patience while i got you the response from the experts. Here it is:
Phosphate washes like After Blast work well if you plan to powder coat or do not plan to prime your parts right away.
But I would use either acid etch primer or a good epoxy primer if you plan to prime and paint parts and avoid a phosphate wash completely.
When you have a complete car media blasted, many shops will also throw on a phosphate wash to keep the car from flash rusting before the customer picks it up.
I generally plan to be ready to pick up the car from the blaster the moment it is done and am ready to throw it into primer.
For large area coverage I generally use PPG DP 90 epoxy primer after I condition the metal using a 3M rust & paint removing disk and wash the surface with PPG Acri-Clean. For small parts or spot repairs I often use SEM self-etch primer.
Phosphate washes are designed to clean and etch the metal in preparation for primer. If you do choose to use them I would next apply an epoxy primer as opposed to a self etch primer.
Wrench Safe,
Mark
Classic Car Restoration Club
what grade sandpaper is needed to sand paint that’s already on the car for repainting once the sanding has been done do the car have to be primed before painting
Dear Cedric,
Thank you for your patience while I got the response from the expert, Here it is:
Generally we use 320 or 400 grit to prep old paint for repaint.
Good paint adhesion is as much a mechanical bond as it is a chemical bond, so sanding with a finer grit paper may actually shorten the length of time your paint remains attached to the old paint. The new paint needs a little tooth to grab onto and hold it secure to the finish.
Wrench Safe,
Mark
Classic Car Restoration Club
Hi What’s the next step after selfech priming ? Can we go ahead and start adding are first coat or will we need som other type of regular primer ?
Hello William,
The Self Etch Primer is a good first step for bare metal, or an Epoxy Primer. Typically the next step is apply a primer surfacer, 2-3 coats then block sand with 320-grit. This helps remove sanding scratches and small surface defects. I then use a primer sealer or epoxy primer to seal up the surface then apply the top coats.
Hope this helps,
Mark
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Is it better to apply body filler before or after self etching primer? Will self etching primer work correctly over body filler?
Hello,
I do not recommend using body filler with self etch primer. I only use self etch on bare metals. If you plan to do body work after priming, epoxy primers are a better choice.
Hope this helps,
Mark
Classic Car Restoration Club Video Membership
Mark, I’ve got some bare metal panels that I’ve been working on but won’t actually get to base coat painting for quite some time (probably months or up to a year). Is the self etching primer something I can spray on to protect it from rust and leave it until I’m finally ready down the road to apply the high build primer?
Hello Rick,
Yes the self etch primer would be a good choice, If you’re going to prime out an entire fender, door, etc. another good choice would be to spray it with a two-part epoxy primer.
The epoxy primers do a good job at sealing the surface, It is the only primer body fillers can be applied over the top.
My general rule of thumb is, If the area to be primed is over a couple feet square, I prefer to mix up some epoxy primer for bare metal.
It’s also important to remember that no primer is meant to be a top coat and they lack any real UV resistance.
If your car is going to be outside during the restoration process you may need to re-coat some of your primed areas.
Hope this helps,
Mark
Classic Car Restoration Club Video Membership