To prime or not on blasted chassis parts?

[Tom Elliott]

What do you all do on your chassis parts (axle's, brake parts, steering parts, etc.) after media blasting? Do you prime then paint or just paint a couple coats of good paint? Driver not a show car. Thanks, Tom

[tbirdtbird]

if you went to the trouble to blast, then protect your investment of time and money and digging sand out of your ears and eyebrows.

Passify (inactivate) the steel using a phosphoric acid wash such as Ospho then use a good primer under your topcoat. else the topcoat is not long for this world. If you cannot get your head around the phosphoric acid step (I get hate mail on this every time i mention it) then at least prime it!!!!!!

[bobusnick104]

Using an etch solution is always a good step. On my driver, I blasted, etched, and used an oxide primer before the black top coat. Driver as it is Rustoleum was fine. I can wipe it down and use mineral spirits to remove any oil and grease. Now on the other project, it will all be epoxy. That's almost bullet proof.

[Bruskie]

I like a good self etching primer

[barkleydave]

Rust Oleome has new Etching primer for aluminum and steel. I have used it on bare steel and then overcoat with epoxy or high solid enamel. So far I have had some of it outside for 2 years and holding up fine.

[Kurt in NJ]

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I use aproduct called "Picklex20" on all the blasted parts, when I get enough done to make it worthwile to prime I use epoxy primer, the picklex20 only parts can hang waiting for years and not rust, any repairs can be done, welds better ---I have some parts that I havn't got to that have 5+ years hanging out still looking freshly blasted ---a quick scrubbing with a skotch brite pad and ready to paint

[edmondclinton]

Originally Posted by Tom Elliott

What do you all do on your chassis parts (axle's, brake parts, steering parts, etc.) after media blasting? Do you prime then paint or just paint a couple coats of good paint? Driver not a show car. Thanks, Tom

I always use a 2 part DP epoxy primer made by PPG (Ditzler). It comes in black (and other colors) and you don't have to top coat unless you want. It's water proof and extremely durable.

[SeaSlugs]

I just blast, wipe down to remove all dust, then POR-15 everything... wont ship when hit with a hammer so i figured it can repel road rocks...

[jw hash]

if the parts are going to get painted, I use DP90 primer it is black. and store them away. then when it is time to paint the parts. put a thin coat of DP50 and paint right over it.

[Kevin in NJ]

Etching primer is not a good solution. You do not need the etching as the surface is mechically etched and it does not do a great job of protecting the metal. Worse yet is the etch primer is often not applied right and it is common to see failures of the paint at the etch primer. That is the next layer does not attach properly. You can see this on restored cars by the chips with etch primer visible.

Depending on what you need to do to the metal you want to either prime with epoxy or use a product like Pickelx20 (ospho might also work).

Epoxy will create a very tight bond to blasted metal assuming you also properly degrease the surface. The problem with epoxy is that you must put the next layer of paint on before you get out of the recoat window. Failing to do this then you should sand the surface then put another layer of epoxy then move onto the next coating you are putting on the part. If you intend to do bondo it is best to do it during the re-coat window too.

PickleX20 is a light etching polymer based surface prep. That is it has some phosphoric acid and some other chemical magic. This means that you do not need to worry about neutralizing the acid on the surface like plain acid treatments. Keep in mind epoxy paints will not cure when on an acid surface leaving you with uncured paint at the metal/epoxy boundary. I have not used Ospho, but the instructions indicated you do not need to neutralize it.

As in all cases read the directions.

All the above information is based on discussions with manufacturers of the products or reading technical information on those products. It is not my opinion and if requested I can give you sources for my information.

[Terry, NJ]

Kevin, I am using a phosphoric acid type product. But it leaves a whitish film on the work. How does one clean this film off the work without removing the affected metal? I washed this material off the piece with water, but I still get this film. What should I do, Just paint over it?
Terry

Originally Posted by Kevin in NJ

Etching primer is not a good solution. You do not need the etching as the surface is mechically etched and it does not do a great job of protecting the metal. Worse yet is the etch primer is often not applied right and it is common to see failures of the paint at the etch primer. That is the next layer does not attach properly. You can see this on restored cars by the chips with etch primer visible.

Depending on what you need to do to the metal you want to either prime with epoxy or use a product like Pickelx20 (ospho might also work).

Epoxy will create a very tight bond to blasted metal assuming you also properly degrease the surface. The problem with epoxy is that you must put the next layer of paint on before you get out of the recoat window. Failing to do this then you should sand the surface then put another layer of epoxy then move onto the next coating you are putting on the part. If you intend to do bondo it is best to do it during the re-coat window too.

PickleX20 is a light etching polymer based surface prep. That is it has some phosphoric acid and some other chemical magic. This means that you do not need to worry about neutralizing the acid on the surface like plain acid treatments. Keep in mind epoxy paints will not cure when on an acid surface leaving you with uncured paint at the metal/epoxy boundary. I have not used Ospho, but the instructions indicated you do not need to neutralize it.

As in all cases read the directions.

All the above information is based on discussions with manufacturers of the products or reading technical information on those products. It is not my opinion and if requested I can give you sources for my information.

[Big hammer]

My chemically striped parts had same coating, I just washed off with wax and grease removed as per the man who striped my parts, frame,fenders,body panels,etc

[tbirdtbird]

In my opinion the Ospho directions are to be taken with a grain of salt.
We learn more from the old timers than we do from any printed instructions. I have been doing paint and body work for more than 40 yrs, while standing knee-deep in salt back in new england (hmmm do they get any snow there? Can't quite recall....maybe that has something to do with the mountains of road salt that you pass by on the highways there?).

I have never 'neutralized' Ospho or any other brand of phosphoric acid, or tried to wash off that white-ish layer. I use it half-strength, and I WANT that white-ish grey-ish color because that color is the iron phosphate layer. I would never try to wash it off. It represents an outer jacket of passivated (inactivated) steel. It is the best prep you can give and any type of paint bonds very well to it. We continue to prep all panels, parts, and paint jobs in this shop this way. Never a failure.

I shot my A 25 yrs ago using these prep methods. There are no chips, lifts, bubbles, or any other kinds of flaws on the surface today. It looks like it was just painted.

I learned these methods from a high-end restorer of Packards a long time ago. A guy who was high on my list of knowledgeable old-timers.

Bottom line, do it however you want. Your car, your hard-earned money for the topcoat.

[townsedan29]

PPG does not recomend any acid product on sand blasted metals also most epoxy primers are not recomended over self etch

[Kevin in NJ]

Originally Posted by Terry, NJ

Kevin, I am using a phosphoric acid type product. But it leaves a whitish film on the work. How does one clean this film off the work without removing the affected metal? I washed this material off the piece with water, but I still get this film. What should I do, Just paint over it?
Terry

Terry, I do not know the answer to your question. I generally scotch brite pads on the metal I have used PickelX20 on because they were laying around for quite a while till I got to painting.

Call the company and ask what the white layer is and how does it affect the adhesion of the paint. Be sure you are talking to a technical person that understands the chemistry.

My main concern would be when using epoxy paint. If that layer is acidic then it could prevent the cure of the epoxy or plastic fillers at the interface. The other paints just need the proper 'etching' for a rough enough surface for the paint to stick to the metal.

[Terry, NJ]

Not to hijack this thread, But to expand to discourse! I started looking for the spec sheet and found it, It's DuPont 5717S "metal conditioner" and the directions say to apply it with a scuff pad (Scotchbright ?) and wash it off. But it doesn't say leave a thin film or get it all off. Dammit! You'd think they would tell you what you should wind up with. Terry

[edmondclinton]

Originally Posted by Kevin in NJ

Epoxy will create a very tight bond to blasted metal assuming you also properly degrease the surface. The problem with epoxy is that you must put the next layer of paint on before you get out of the recoat window.

Not really a problem if one plans because the recoat window is 7 days.

[Kevin in NJ]

Originally Posted by edmondclinton

Not really a problem if one plans because the recoat window is 7 days.

Unfortunately some of us do not have that kind of time. I spent a weekend blasting all the metal then spent a few years getting the work done on the parts. Of late, I have been taking 15 mins here and an hour there. Really takes a lot of time move a project along at these rates, but what can I do family comes first.

That is why I go out of my way to give the options. So people can figure out what will work best for their situation.

[glenn in camino]

On my sand blasted chassis parts, I use one sprayed coat of Rustoleum red primer, and 2 sprayed coats of gloss black Rustoleum. Semi gloss on the frame.

[Doug in NJ]

Originally Posted by townsedan29

PPG does not recomend any acid product on sand blasted metals also most epoxy primers are not recomended over self etch

PPG's data sheet for DPLF epoxy primer says: "Chemical treatment or the use of a conversion coating will enhance the adhesion and performance properties of the finished system." Isn't a "conversion coating" acid-based?

Doug