[apehanger mike]

i'm using a all in one primer called " rust defender " by clausen and after sitting out in the weather for approximately 30 days, it developed raised bumps all over it. clausen said it was from water contamination so i removed all of the product and redid it.my question is what about some of my other parts that have been stored inside ? will they develop pimples after a while or how long does this take to show up if it is going to happen ?some of these parts were done 4-5 months ago with a different batch of material .

[willys36@aol.com]

Sounds like maybe water contamination but more likely solvent pop. Did you thin it according to instructions? Do you have good water separation in your air supply line? If it was water, you should see little globs sitting on the surface as you spray the paint on the car. As the paint dries and the water evaporates, that defect leaves pock marks immediately. Solvent pop blisters can show up quite a bit later in the drying process. If that is the case, you learned a good lesson why not to over-thin your paint!

A defect that looks a lot like this is rust formation under the paint but that usually takes many months or years to develop so it isn't likely your problem.

[apehanger mike]

this may be rust formation . this product specifies that no metal treatment be used under it as it has a treatment built in. these bumps showed up within 30 days of application and was only thinned with one ounce thinner to 32 ounces of primer. catalyst measurement was pretty exact also . there was no actual rust on these parts before they were sprayed but when it was removed there were slight rust stains underneath.

[willys36@aol.com]

I doubt it was rust. When rust blisters finally come to the surface, there is usually very heavy metal loss that forms a rust glob that forces the paint up. Although rust stains under fresh rust preventative is not a good thing, I doubt it contributed to your bad complexion.

[BarryK]

Rust defender on its own is an almost impossible product to
solvent pop. Don't know how it can be done!

First of all if the rust defender was applied over bare metal and the panel was left outside for a month the polyester soaked up the water and rust does not have to scale to form gas and create bubbles.

Only other thing is if rust defender was applied over ACID ETCH primer. That will do it.

"Yes I said that and don't care what the tech sheets say!"

[apehanger mike]

Thanks everyone, I don't know if I'll ever find out exactly why this happened but I can only hope it doesn't happen with my other panels after I get some paint on them . Is there anything I can do to force this to happen or not so I can be sure ?

[BarryK]

If the other panels were left inside and do not have acid etch under the primer you have nothing to worry about.

If they were outside in rain, I would strip them and start over.

Remember this primer is nothing more than spray body filler and will not stand up to water long.

I should add the third thing that could cause this type of primer to do third this, is if the metal was acid treated and not neutralized properly.