Self-Etching Primer?

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

gregnash

gregnash

Anal Retentive Analyst
10 Year
Joined
Nov 3, 2011
Threads
176
Messages
12,365
Location
Carson City, NV
Ok so what am I doing wrong here..
Last summer I took my front lower cowl off my FJ60 (the part that the headlight squirters mount to) as I had a few rust spots.
I took it down to bare metal, cleaned well, took out ALL rust including the one small section that was rusted through. Then threw a few coats of self-etching primer on over the cleaned metal. However now I am starting to see rust bubbling through again.

What did I do wrong?
 
A good while back I worked under a guy who was a master machinist. He always said paint breaks down on corners, so he had me sanding and grinding them off.
He also used major league degreasers then metal acid etch before painting.

Like you I have used self etching primers and have had similar disappointments.
I am now back to trisodium phosphate and acid etch. I then prime with 2 part epoxy primer. It is more expensve and using my spray gun means more clean up time. I haven't had problems like the rust resurgence.
 
Yeah don't have the space or the time for something like that.. I figured with the metal prep that I had done it would get ride of the rust but apparently not? Guess it is going to be an additional step of using something like a rust mort or chassis saver/por-15 to base then prime for this stuff?!
 
jblueridge said:
You can get the 2 part epoxy in special compartmental spray cans.
2K Aerospray Epoxy Primer Black

The acid etch is at places like Home Depot. Phosphoric acid leaves a phosphate film to promote adhesion.

Klean-Strip 1 gal. Phosphoric Prep and Etch-GKPA30220 - The Home Depot
Click to expand...

So with the Klean-Strip do you just spray/wipe it on, let it sit for a minute or two and then wipe off? I know that there are some areas that I need to hit with something like OsPho so that I can stop the rust but haven't picked the stuff up yet. Would this stuff serve the same purpose?
 
Your post doesn't mention that you painted over the primer - is this the case? Primer isn't intended or suited for use without a top coat.
 
Nope, never painted over it just did the self-etching primer... So basically that is where the primer was more than likely thinner and the metal started rusting there... Looks like I will be cleaning it again, treating with something and then priming and coating. When I did it I had not planned on it being primered forever, the plan was for the whole truck to be Monstalinered in the fall but then other things happened and I was out of commission until November.
 
Some primers can protect the substrate without being topcoated. Self etching primers aren't one of them. They also need to be coated with a surface peimer before applying most paints. Do yourself a favor and coat with an epoxy primer and then paint.
 
Yeah, self-etching primer needs to be top coated. It’s basically porous and acted like a sponge, holding the water against the metal and allowing it to rust again. So you’re back to square one - clean it all down to bare metal, self-etching primer (or epoxy primer), and top coat.
 
Last edited:
Ok thanks for the help guys.. that makes a lot of sense and didnt realize that self-etching primer/primer were basically porous.
Looks like I got a little project for myself this weekend. Will see how bad the rust is, thinking since it is basically just showing through the thin(ish) layers of primer that it is hopefully just surface rust. If not, at least now I have the welder and can get it taken care of if there is a hole.

Going to have to grab myself a bottle of the Kleen-Strip as well.
 
Most primers are just that - something to stick to the base material and promote adhesion of the subsequent layers while offering no “protection” itself. The qualities that make it a good primer actually work against it offering protection. The porosity allows the subsequent coats to bond to it. This is also why you have a window to recoat an epoxy primer - it still provides adhesion before it fully cures but after that you have to mechanically scuff it so that subsequent coats can bond to it.
 
Ok thanks for the info @PAToyota ... Never painted anything like this so I wasn't sure exactly what was going on. Soon as the rain stops here I will probably trying care of it to get rid of any excessive rust.
 
Thanks for catching that - I corrected my response. I meant to say one or the other - not both.
 
Thanks again... I am basically trying to do this via rattle cans for the time being until I can get around to actually doing the ML over my entire truck (at least that is the way I am leaning right now). While I do have a compressor with adequate power to do the spraying the thing I really don't have is the space to do a paint job. I would love to spray my truck but it just isn't in the cards (hence leaning towards the ML).

Since I am still in the process of fixing the rust on my 60 I am taking care of things here and there as I get the time. I want to be sure that the items I hit, don't start rusting again before I can get around to painting.

And main reason that I don't necessarily want to spray in the garage is that our oil heater is in there and don't want to start any fires with the "paint fog". One of my club members had recommended that I strip the truck the night before and then early the next morning (during the summer) I fog the entire truck that way it is outside and since it will be warm and pretty much no breeze I should get an acceptable paint job. He suggested doing this with a single stage that way I would not have to worry about priming, scuffing, etc. it would basically be a one and done once I was happy with the coverage.

Thoughts on this process. While I love the ML products I am having a hard time with the available colors, plus I like the shine of a decent paint job. If I do paint, I will probably use something like the Sherwin-Williams industrial/farm enamel paints since I have a SW right by my office and they "should" protect well against NV pinstriping.
 
You still have to prime and scuff for a single stage paint to stick - single stage refers to color only - no clear coat. Clear coat would be the second stage.
 
bryson said:
You still have to prime and scuff for a single stage paint to stick - single stage refers to color only - no clear coat. Clear coat would be the second stage.
Click to expand...

Yup. Prep is still the same.
 
Ok well I am thinking I may grab one of the HVLP guns from HF to play with. I have a spare door and whats left of my original rear tailgate to practice on. Passenger rear door has a nice sized rust hole in it that the PO covered with mud and paint. It is in the curved section that I CANNOT recreate so I ended getting a door for the price of beer from a fellow member. Door is white and my 60 is grey-ish so I need to paint the door. I have a dent that needs to be removed and then scuff everything to accept primer and paint.

Looks like I have some practice pieces to work with now just have to wait for the weather to be above 40*ish.
 
You must log in or register to reply here.

Share this page

Back
Top Bottom