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Non Locost Question
The Doc - 30/6/08 at 08:13 AM

In the decades I have been doing up old knackers I have never really resolved this question:

When repairing rotten bodywork

Filler then primer or

Primer then filler?

I have generally thought it best to use rust arresting primer, then filler but on new metal not so sure.

Any body repair experts out there who can advise?

TA

Mike

r1_pete - 30/6/08 at 08:22 AM

My view when restoring bodywork, cut out the rust, weld in new metal, never create more layers of metal than original. Grind and tidy welds, 40 grit DA the bare metal, filler, etch primer, primer, finish. Many etch primers wont take polyester fillers on top.
Rgds.

02GF74 - 30/6/08 at 08:41 AM

hmmmm, I have always painted the metal with zinc primer or similar then put put filler on top.

pimer/filler primer and paint on top of that.

jabs - 30/6/08 at 09:49 AM

Was taught at college, on a car restoration course, to apply filler to bare metal to get a direct bond. otherwise you are just bonding to the paint layer

Delinquent - 30/6/08 at 10:03 AM

quote:
Originally posted by jabs
Was taught at college, on a car restoration course, to apply filler to bare metal to get a direct bond. otherwise you are just bonding to the paint layer


ironically, I was told NEVER to apply the filler to bare metal for exactly that reason - I was told that the best thing to do is to use either an etch or an epoxy primer first - with preference given to the epoxy primer.

r1_pete - 30/6/08 at 11:35 AM

I guess the real answer is there isn't a right or wrong way of doing it, as long as the materials are compatible, and the repair is invisible.. Only time would tell which fails first if at all.

worX - 30/6/08 at 12:08 PM

I was told that you shouldn't apply filler to bare metal as it is porous, so by the time you come round to painting it, it has already drawn in a small amount of moisture and so will therefore start to corrode the area you've just repaired from behind the repair...

Steve

chrsgrain - 30/6/08 at 01:04 PM

quote:
Originally posted by r1_pete
My view when restoring bodywork, cut out the rust, weld in new metal, never create more layers of metal than original. Grind and tidy welds, 40 grit DA the bare metal, filler, etch primer, primer, finish. Many etch primers wont take polyester fillers on top.
Rgds.


I'd agree - but use lead loading in place of the filler.... much better job....

Chris

r1_pete - 30/6/08 at 02:14 PM

Yep I agree Chris, tried lead a few times, never seem to get quite enough in, whether its just a skim or a dollop required, end up with a bit of filler rather than starting again.

Mark Allanson - 30/6/08 at 07:00 PM

Porous fillers went out with Austin A35's, if you were to etch then fill, when you block out the filler, you would remove the surrounding etch so no point putting it there in the first place.

Bare metal with all welds fully dressed with 80g. No pinholes in the welds or the surrounding steel. never fill onto unkeyed existing paint. Always cover filler with a stopper layer.

We use about 50kgs of stopper a month, but only 5kgs of filler, I personally never use filler, if a dent is that deep, it needs planishing.