Repro bare metal prep

[crumbaa]

I know I am asking allot of paint and body question, but this is an area where I have very little experience, and it is too expensive and too much work to have to do it over, so I hate to get it wrong.

I think I may have messed up. My original running boards were welded at the front fenders so I sacrified the running board so I could save the fenders. I ordered repro boards. We are a ways out from laying paint down and I was afraid of leaving them bare and getting rust. So I got some etching primer (the kind recommend buy the guy that is shooting the final paint for me), used degreaser and then denatured alcohol to prep them and shot them with primer. Now I am worried that maybe I should have rubbed the bare metal down with sandpaper before cleaning and priming. Worried that they may have too slick to hold the primer properly.

Our plan is to final fit and align all the body panels and doors before we take is all in for final prep and paint. Should I blast the primer off the boards after we get done final fitting and re-prime them? Or is it OK to sent them to the painter for final prep and paint?

/Tony

[John Duden]

what I have been doing is with clean bare (new) metal, is taking a red scotch bright and rubbing it down really well. you could take paint stripper and apply it and and let it soak and then it will wipe right off. Then wash them with dawn dish soap and hot water, Dry them and rub down good with a red scotch bright or a fine sandpaper, and reprime.
I had to paint a little on my new cab corners for my truck and then decided to go a different route with the paint and assemble. So this is the process I used. It worked great!
John

[SkipShift]

Your painter gave you good advice. Since you used etching primer there was no need to scuff bare metal. Etching primer is made to stick to smooth bare metal. Fit and send to paint. I'm sure painter will confirm.

[Kevin in NJ]

Paint sticks by being properly etched so that the paint has scratch to attach. This can be done chemically or mechanically.

Etching primer is designed to prep metal for paint so that a mechanical (costly labor) etching is not required. Etching primer is often used wrong and I have seem a lot of cars where the paint came off leaving the nice etch primer exposed. That means the next layer of paint failed to adhere to the the etching primer. Generally, you do not want to use epoxies over etch as the acid prevents the epoxy from curing at the interface.

I was sold on the idea of etching primers by the local experts at one time. But stuff did not add up. Lots of guys use it thinking it deals with the surface rust issues. It is not for controlling rust, it is only for getting the surfaces prepared for the next level of paint. After seeming so many paint failures at the shows I question how good it really is as a primer. I will not use it. You are much better off properly sanding the surface and laying down epoxy direct to the metal.

Now one of the issues is how it is supposed to be used. I just double checked off the variprime instructions. Etching primers I believe have a very short recoat window. That is you must spray the next coat within 24 hours. After this period the paint is no longer open to bonding to the next layer of paint. You then must mechanically etch the surface (sand it) which you are not supposed to do with etching primer. I believe too many guys violate the recoat window rules which causes the failures. They coat the metal with the etching primer and then some time way past the recoat window they try to put the next coat on and that is not a good thing to do.

BTW, epoxy is similar in that you must paint the next layer in the recoat window or the next layer will not stick.

So the moral of the story.

Read, understand and follow the instructions the manufacturer tells you to do. You would be surprised how many seasoned professionals give you the wrong advice.

There are many right ways to paint something. They all involve reading and following the directions.


Oh, that goes for the cleaning of the metal. Solvents are for dissolving stuff. Cleaners move the contaminates to the surface so they can be lifted off.
So using alcohol may just spread the contaminates around the surface and not effectively clean. So you are best to use the proper removers. I have heard of paint failures traced to not using the correct cleaners.

[RobertB]

So may I ask a related question on this thread?

I am about to have a small car (MG) painted. I can't decide on a base/clear coat, or just a two part enamel. I'm asking now because I will eventually have the same question about my Model A.

If I do the two part enamel now (cheaper) can I come back later with a clear coat? Factory clear coats around here have a habit of flaking off after a few years on the hood and roof and trunk lids. On the other hand, they do look good.

Decisions, decisions...

[BRENT in 10-uh-C]

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Originally Posted by RobertB

So may I ask a related question on this thread?

I am about to have a small car (MG) painted. I can't decide on a base/clear coat, or just a two part enamel. I'm asking now because I will eventually have the same question about my Model A.

If I do the two part enamel now (cheaper) can I come back later with a clear coat? Factory clear coats around here have a habit of flaking off after a few years on the hood and roof and trunk lids. On the other hand, they do look good.

Decisions, decisions...

The real question is what are you trying to achieve by using Clear?

On modern vehicles, the reason is a basic two-fold answer. First, the pigment is what creates cost, so using a 'minute' amount of pigment (i.e.: base) and then using a clear over that saves money. The Second side is the Clear is more resistant to UV thus protecting the actual color longer (less premature fading).

So, is your MG going to be protected from UV by spending most of its' life in a garage? If so, the BC/CC is of no benefit. I will also tell you that the 2k Enamel or Urethane is MUCH easier to repair chips in the paint for most hobbyists.