professional input please - product sequence over bare steel

[haycait911]

I'd appreciate the opinion of a few of the other pros out there that have more restoration experience than I do.

here's the scenario, car is in bare clean steel, metalwork done.

what I've always done is:

any plastic filler work. then epoxy, then high build primer.

but this is more of a collision repair procedure. as I'm doing just restorations now I'm thinking of changing my procedure to suit.

again, from bare steel:

epoxy first. then spray polyester filler. then do any plastic filler work, then either go directly to high build primer. or optionally, put on a coat of spray poly filler, then high build.

any thoughts? I like the idea of all bare steel getting a coat of epoxy before anything else. I've talked to my paint reps. but again, they're really more involved in the collision repair side of things.

any input much appreciated. thanks, Don.

[Iciclehead]

I only know Sikkens products, but they like to see an etch (basically a chromate product) that gets misted on to galvanized surfaces. I would have to dig up the name of the exact product, but essentially it was a very thin product that apparently dug into the galvanized coating for strong adhesion and provided a good substrate for the high build primer I put on next.

Can't speak to the filler stuff, I only use lead and then a bit of putty here and there....and of course the lead work is done before any of this stuff.

Dennis

[962porsche]

you can not use a polyester spray filler over E-type primers .
it will stick for about a year or two then will delaminate in sheets .
a spray filler works great for fiberglass and other composite materials or just over bare steel but not so good at all for going over any etch or epoxy products .

the proses is the same no matter if it's a collision repair or a resto .
bare metal you spray a E-primer then a high build or medium build primer over it .
there are high build primers out there that will give you about the same mill build as a high fill polyester spray filler .

[haycait911]

Dennis, where are you located?

these are older cars so no galvanized steel anyway. I've used etch primer but the ones I've used were non-catalyzed. I'm not real comfortable putting a non-catalyzed product as the first coat under catalyzed products. I'm a big fan of epoxy.

interesting info on poly spray filler over epoxy. I've used it before but both were glass cars, a '57 Vette and a Lotus Elan, and directly to the base fiberglass. used it there to give a stable base for the high build primer. in this case I'm not looking for mil thickness but more for the previous reason. to give a homogeneous surface to put high build on.

[962porsche]

no you do not want to use what is called a reversible product under a hardened or catalyzed product .

spray fill is made for fiberglass . non of the fiberglass cars are made out of epoxy fiberglass resin . they are made out of polyester resins .
you will find most boats are made out of vinylester or epoxy as they hold up to salt better then polyester does .
so spraying a high build polyester filler over polyester resin is fine .
how ever spraying a epoxy primer over fiberglass is very pointless .
there is no metal you need to worry about so the chromates in the epoxy primer will eat there way into the resin of polyester resin .

the only time you would really need a very high build spray filler is when you have to block the hell out of some thing . other then that it's not needed !
just a good old high build 2 part primer is all you should need .
at times some things will need to get double primed with a high build primer but again all you need for that is just a good high or medium build primer .
more product is never better ! the less mills you put on a car the better it is .
primers do not protect the substrate the top coat does that .
the primers are for giving some thing to have the top coats stick to .
yes a chromated etch or epoxy primer does give protection to bare metals but not what most people think it does .
if you just etch primed a panel and put it out in the weather for a year of so it will start to rust under the primer .

[haycait911]

thanks 962porsche. high build primer has always worked for me so I'll stick with what I know. I was kind of baffled why guys I talked to were pushing the spray poly. my usual prime procedure is to epoxy over bare steel and filler work. sand, then three coats of high build. block with 180 then 240. another 2 or 3 coats of high build depending on how the blocking went. then block and sand to final grit.

[962porsche]

that is just how you do it !

I have found over the years that when you want your work nice and straight it's best to build the material slowly . a heavy build spray filler is just very thick ! most of the time overly thick for most needs .
yes on a composite panel it's one thing as even the best are wavy so you spray 3 coats of spray filler and 80% ends up on the floor after your finished blocking .
but when it comes to sheet metal it's a hole other story .
the metal should be dam straight to start with before you spray any product down .
if you need a spray filler on sheet metal you should step back and fix the reasons why you would need to do that .
one thing I would see all to often is people will try and fix there bad body work with primers
primers . many so called body men will also do it and it's just wrong !

priming is no different then spreading body filler . you want to build it in layers not all in one fat coat .
so double priming is more then ok when it needs to be done .

the standard rule is no more then 14 mills of product on a panel .
spray fillers will tend to push that rule to the limit .
now if they say you should strip a panel if it has 14 mills or more then why do so many people think porking on more products is a good thing ? when in fact it's worse !
the less products you put on a panel the better it is all around .
it will last longer not chip as ez and protect the substrate better .

i'm not saying you should never use a spray filler on metals there is a time and place were you can and should use them .

two weeks ago I had a front fender for a 911 that had some bad rust pits around the head lamp .
I blasted the area clean but there were so many rust pits left did not want to spread body filler over the area .
because it was very clean after blasting I sprayed 3 coats of spray filler over the area (just the area were the rust was ) blocked it down to bare leaving the spray filler in the rust pits .
then finished the repair as you would any other repair .

spray fillers are what the name implies ( filler) .