I am currently working on the undercarriage of my '67. The whole thing was sandblasted to see what we had, and then we did the metal work. Well since then some surface rust developed here and there, and I was wondering how best to take care of it. I am planning on next smoothing out some patch areas with USC's Duraglass, and then using a self etching primer followed by a sealer and then I'm not sure what I want to use for a topcoat. I know metal conditioner is out of the question when using the etching primer. So what do you think?

Thanks for your time,
Steve

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MY PROJECTS
1967 Chevelle SS396 - Currently under construction

1970 Camaro RS Z28-
Currently thinking about it

1986 IROC Z28-
My daily driver, always under construction.

eSteve, right off the bat, I am not a big "metal conditioners" user. Metal conditioner can be used with an etching primer though. It simply has to be a conditioner not a converter, that DOES NOT leave a phosphate coatng on the surface. A "cleaner" or "conditioner" is ok, but not a "conversion coating". I don't know many brands but M-S 6878 is an acid based cleaner and you can shoot etch primer over it.

But lets see some other ways to do this.....

If the rust is VERY minor like a discoloration, scuffing it it well and then an acid etching primer has never did me wrong. It IS a converstion coating, leaving a phosphate coating on the metal.

You could also treat it with a converstion treatment and then epoxy prime/sealer.

I will tell you, if it were me, I would scuff it well, use a vinyl wash etching primer (contains PVC), black epoxy primer and then a SS urethane black top coat. This is the system of choice on many truck fleets that are up against much more adverse condtions than your Velle will ever see.

You can shoot some etching primers over CURED plastic fillers, so you could do your repair work and then etch and prime.

By the way, the etch primer and epoxy primer/sealer need NO sanding. That is one reason this is a good way to go. Be sure to read the tech sheets, the vinyl wash for instance (M-S 8827) has only a four hour window before you HAVE to prime it.

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1965 Buick Gran Sport Convertible
1965 Buick Skylark H/T
"Fan of most anything that moves human beings"

Thanks Martin, I was concerned about using the etching primer over the filler, because I guess it's not the ideal method. I'm using DuPont products, for no other reason than the place I get it is helpful when I come in with a million questions. I have some DuPont Variprime, and the grey prime-and-seal that I used on my rad support, but it's not enough for the whole bottom so I'll have to get more anyhow, so I'll see what they carry in a vinyl wash etching primer.

What is the reason for the addition of the PVC? Is it simply for durability? And I guess the reason for the black epoxy is in case of paint chips down to the primer it wouldn't be as noticeable? And one more question, what does the SS stand for in SS urethane?

Thanks for your time, I appreciate it.
Steve

Steve, the Variprime is a good choice. You can spray the Variprime right up to the plastic filler (though I have shot it over cured filler without a problem). The PVC is a plastic that coats the surface that protects the metal. The SS stands for Single Stage, as opposed to base coat clear coat or BC/CC.

Yes on the black primer reason but also it is just BETTER. Prime-n-seal is good product but doesn't provide the "cush" that an epoxy primer does for chip resistance.

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1965 Buick Gran Sport Convertible
1965 Buick Skylark H/T
"Fan of most anything that moves human beings"

That clears things up for me. I guess then I'll try and avoid spraying the etching primer over the filler (you know I never even thought about spraying it right up to the filler... duh). This undercarriage is tough work!

Thanks again, I designate you official body shop forum guru http://www.chevelles.com/forum/wink.gif

Steve

------------------
MY PROJECTS
1967 Chevelle SS396 - Currently under construction

1970 Camaro RS Z28-
Currently thinking about it

1986 IROC Z28-
My daily driver, always under construction.