Advise on prep for metal?

Tux05

Original poster
Member
Jun 6, 2016
38
Northern ontario
On my 05 envoy I have painted rust spots a number of times with expensive can paint and cheap can paint. Each time the result was the same about two days latter the rust showed through the paint. I have Sand blasted it down to clear metal (or so I thought) primed it and painted with three coats let them dry between coats but always the rust comes back.I have painted years before and never had this problem but I am far from being a pro. Is there an acid wash to use and if so what is the best. I think I have to neutralize the rust first but as I said I have never had to in the past. Thanks for the help. Tux05
 

Sparky

Member
Dec 4, 2011
12,927
Where is this rust at? You may be fighting rust not on the surface that you're working on but from behind it. Door edges/seams are well known for that sort of thing.
 
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Tux05

Original poster
Member
Jun 6, 2016
38
Northern ontario
The rust is over both rear wheel wells and bottom of tailgate this is good advice I have sand blasted the inside metai on the tailgate but never got in between the two layers of the tailgate. This would be hard to do can the inside be greased or oiled? Thanks
 

mrrsm

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Oct 22, 2015
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Tampa Bay Area
There are a few "Rusty Metal" Paint Treatments with POR -15 (meaning Paint Over Rust) probably being the most used. It treats rusted areas in order to bind with the semi-cleaned Rusty Surfaces and inactivates the O2 + Ferrous Metal Rusting Chemistry. You could start with a POR-15 "Sample Kit" and then work in a small area to determine the results.

It is important to follow the Use Instructions 'To The Letter' if you expect actual good results. There are quite a few Youtube Videos that show how to use this stuff... and of course... afterwards, you would STILL have to apply the appropriate GM Factory paint over any POR-15 Treated surfaces. A little can of this stuff goes a remarkably long way... :>)

 
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HARDTRAILZ

Moderator
Nov 18, 2011
49,665
Chassis Saver is a good paint for over rust.
 

DocBrown

Member
Dec 8, 2011
501
X2 on POR-15, excellent product, as stated you need to follow instructions closely. However as Sparky said, if the rust is coming through from behind you're fighting a losing battle. Your best bet is to cut out the rusted area and form custom replacement panels to weld in.
 
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Tux05

Original poster
Member
Jun 6, 2016
38
Northern ontario
Thanks for the info guys it helps. I do not know what I will do the envoy still runs great but there are a few other problems with it so when you ad it all up the cost of repairs keeps climbing.
 

mrrsm

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Oct 22, 2015
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Posting up Fresh Images of those areas is always helpful because takes All of the Guess Work out of what to suggest over time. Good Luck with your SUV.
 
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Tux05

Original poster
Member
Jun 6, 2016
38
Northern ontario
Just an up date on info. I sand blasted primed and painted about 2 weeks ago and no rust has come through yet. When I used a rust preventative primer before the rust showed through in two days. The time used "Rust Killer" in a can so this one goes on with a brush or roller it is made by "Rust Check" in a 236ml (8oz) can. After 2 weeks it still looks good. Hope this may help someone else Tux05
 

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