Self Etching primer reaction

Hotrodvideo

Hotrodvideo

Senior Member
I have an original '32 frame that I had soda blasted and I sanded it down and sprayed Mar Hyde single stage grey self etching primer on it.

in some areas it covers well but in some parts of the frame, the metal is reacting to the primer or vice versa causing it to separate. It almost looks like watered down milk.

It also did this on the '32 wishbone and axle and also on some '40 brakes I'm using.

Has anyone encountered this? Should I be using epoxy primer instead?
 
When you say "causing it to separate" , do you mean it is physically separating or just that it doesn't look like it has coverage?
 
sounds like youve got some grease or oil on there. should have used wax and grease remover. it evaporates clean and quick. also, soda blasting is underkill for something like a frame it should have been blasted with sand which will actually etch the metal then it doesnt matter what you prime it with itll have a surface that the primer can really bite into. also ive heard of soda blasting leaving a residue that can effect paints.
but my guess in grease or oil.
 
Here is a link to a company that I use for all my epoxy primer , clear coat and wax oil and greas removal products. Log into the forum and ask your metal prep questions there and you will get som very informative answers. You can also call Barry ( the owner of the company) and he will walk you through the problem with the correct procedure and product. I love their epoxy primer and clear coat. That is what is on my Vicky avitar and my 356 Porsche.

Hope this helps.



http://www.spiuserforum.com/forum.php
 
here's a pic of the frame when it came back from the media blaster, there was no paint and no rust, it was perfectly clean.

I sanded it down after this picture and then cleaned it with lacquer thinner, I also used acetone on some parts of it.
 

Attachments

  • FRAME.jpg
    FRAME.jpg
    57.6 KB · Views: 63
I can remember reading on the SPI user forum that I posted the link to, that there is sometimes problems with soda blasting and primers. If you do a search on that forum or join it and ask your question there you will get some good answers. That is where I go with prep and paint questions.
Hope this helps everyone.
 
really sounds like oil from ur hands or rags some where... . if there is contamination on the surface it will do what happened to u. use wax and grease remover instead of lac thinner and don't touch it after its wiped down. could also come from ur air compressor, they sell a small filter that screws in at paint gun and is only about 10 bucks never had a problem painting something thats been soda blasted so i don't think thats ur problem hope this helps ..Dave:cool:
 
Hotrodvideo said:
I sanded it down after this picture and then cleaned it with lacquer thinner, I also used acetone on some parts of it.
Click to expand...

Lacquer thinner isn't a cleaning agent even though people attempt to use it as such. You should use products such as DuPont's Prep-Sol and/or Final Klean (DX440 and DX330 are the PPG equivalents) to clean the part prior to priming/painting.

I'd agree with the others in that you likely still have some sort of contamination on the frame in those locations.
 
Soda and acid don't mix well. Mixing acids with bases always make a chemical reaction. I've read quite a few stories about problems with refinishing after soda blast. It is really hard to get the soda off unless you hit it with a phosphoric acid etch solution to sort of neutralize the soda prior to prepping it for paint.

Most self etching primers have a mild form of phosphoric acid in them so they react to the soda right away before the paint can dry.
 
You must log in or register to reply here.
Back
Top