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Spray fillers
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ukdave2002



Joined: 23 Nov 2007
Posts: 4231
Location: South Cheshire

PostPosted: Thu Sep 20, 2012 7:56 pm    Post subject: Spray fillers Reply with quote

In the past I have used a few coats of 2k high build primer when needing to stopper a large area. Typically for panels that have been exposed to moisture and are pitted all over .

Been looking at products like ;U-Pol "Reface " or Mipa P60. Feedback I have had from other a couple of painters is that they are good, but absorb moisture like there is no tomorrow! So need paint within a few hours.

Anyone got experience?

Dave
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Farmer John



Joined: 18 Feb 2010
Posts: 181
Location: Manawatu NZ

PostPosted: Thu Sep 20, 2012 9:28 pm    Post subject: Paint Reply with quote

Hello Dave.
That seems to be the way with body and paint, so much is based on opinion.
I have spent countless hours on hotrod sites in USA trying to sift out what best suits us classic guys. So much of what hotrodders do is exactly the same, really old panels, dents, rust.
Probably better to ask for the milkman's opinion rather than mine, but I have concluded that nothing but epoxy primer is applied over rust free metal, ever. ( No etch for me ) Filling or skimming onto the epoxy.
Rust removal discussion is likely to start a gunfight. Looks like almost anything will work until down to the pitting but sandblasting can distort panels as can heat from any powertool. I distorted one with a rotary knotted-wire brush. Phosphoric acid in conjunction with anything that will get the rust out of the pits is where the work is. Toothbrush, wirebrush, scriber, anything which works. Painstakingly going over the whole panel. For the specks missed, or inaccessible places, the epoxy will provide the best protection possible.
Remember the adage, "if you are not sure, the right way will be the most work", bodywork complies with that. There are no miracles.
All the stuff I have done is still in the shed so have no proof whatsoever just my opinion, and I think that you are on the right track.

John
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Kelsham



Joined: 18 Jan 2009
Posts: 349
Location: Llandrindod Wells Powys

PostPosted: Fri Sep 21, 2012 8:39 am    Post subject: Reply with quote

Farmer John has it right in my opinion.

I too have distorted a panel, in my case by using a polycarbide disc in an angle grinder.

I usually use Jenolite several applications, scrubbing after each application with a small wire brush.

This I carry on with until no more red rust appears on the surface.

I then use Bondaprimer. I know this is old technology, I just find it hard to leave it because I know it works.

Epoxy primer is probably the way to go.

The secret is good old fashioned preparation, mechanical removal of all easily removed rust, and then chemical treatment, followed by painting.

Regards Kels.
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ukdave2002



Joined: 23 Nov 2007
Posts: 4231
Location: South Cheshire

PostPosted: Fri Sep 21, 2012 11:52 am    Post subject: Reply with quote

Thanks for the reply's

Rust isn't the problem as the panels have been professorially dipped and I will treat them with phosphoric acid , followed by an etch primer immediately prior to any painting.

The challenge is the pitting, I could stopper the large pitted area or apply several coats of high build primer, looking at the spec of the spray filler, it can be applied about 3 times thicker than 2k high build. Its polyester based so not much different to filler/ stopper, however its the "anecdotal" moisture absorbing rumors about the stuff that worry me, as any trapped moisture will eventually cause the paint to blister, possibly some months later.

As I use 2k the air is very well filtered and I have a final moisture trap on the gun, the workshop is dry and dehumidified , but I don't have access to an oven, although I would paint immediately.

Possibly I am being a bit paranoid, but know of a couple of cars that had fantastic paint jobs, that were ruined a few months later because filler (not spray filler) had been left exposed for too long prior to painting; in one case it was only a week in a dry spell during summer! (it may have been caused by water in the airline/ paint of course)

Dave
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Desert Fox



Joined: 21 May 2013
Posts: 25
Location: Leeds

PostPosted: Fri May 24, 2013 10:27 am    Post subject: Reply with quote

UK Dave is quite right, blisters can be caused by moisture entrapment. But there can be varying reasons for blisters. Also, it depends on the individual interpretation of the actual problem, for example, blisters or pin holes.

Blistering is commonly caused by

Surface contaminated before painting.
Insufficient / incorrect undercoat
Insufficient top coat
Non-approved thinner - most likely
Non - approved paint system
Exposing the finish to wet weather or high humidity before it is correctly cured
Continuous exposure to severe wet weather and conditions of high humidity.

I suspect that a lot of people use a 1k spray filler which is simply a fast thinner loaded with talc to produce a paste, is cheap and nasty and will absorb moisture. I will only use a 2k primer filler usually a PU that when cured is impervious to moisture.

I have regularly primed a surface, dry flatted and wet flatted, applied the colour and clear in the same day all without the benefit of an oven. and then wet flatted and polished the clear coat the following day. I have never had a return due to paint problems.

The key to a good finish is 90% preparation and 10% application with the correct paint system. Bare in mind, 2k paint will require at least 7 days for a chemical cure before being submitted to extreme weather or a pressure washer!
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