rust treatment

I know this is a little off topic ;-) but I know there are people on this forum who know a lot about this stuff and I have not had much success on other forums. The photos below show where I have tried to address rust that has started mainly on seams in the van (2006 Mercedes Sprinter). At the time I used a wire brush on an angle grinder to take the affected area back to bare steel. In one case I painted Dulux Metalsheild All Surface Primer straight on the surface and then used top coat. It has re-appeared as can be seen below.
Another time I wired brushed back to bare metal as before and then applied rust converter on the rust right inside the seam and then applied several coats of grey car primer from a can straight over the top. When dry I used a spray top coat. I know it looks rough but you can't see the roof ;-)

In both cases the rust has come back, am I doing something wrong, should I be cleaning the bare metal with something before priming. Maybe I am using crappy products?

thanks

What Ramona said. I use swimming pool acid from bunnings, let it fizz for 5 mins or wire brush while its on there as well. Wash it with water and dry with clean rags.
Now check for black rust spots and get rid of them ( i gently use a drill for this )
Repeat the acid, water and clean rags then paint. If there is a join with a crevice or bits you cant get at use penetrol as a primer. It soaks in like wd 40 then sets. Any black spots left will eventualy come back.
Hope this helps

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MichaelR said..
Clean the rust completely back to bare metal, use POR 15+ from Permanent Painted Coatings, in Warriewood NSW, including their metal ready prior to the POR. Once that's done, you'll need a tie coat, then your top coat of choice.

Call, them, they're very knowledgeable.

I have no affiliation, but have restored a few bikes and cars with these products.

yeah, I have heard about the POR 15 stuff, sounds good

Phosphoric acid, wipe of with water, wire brush on grinder, repeat ....... When had enough of that game wipe with metho to remove any lingering water then epoxy resin then paint. A bit over the top for a vehicle maybe but I have great results onboard with this method

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dralyagmas said..
How does this change with aluminium rather than steel?

Phosphoric acid will etch the aluminium. This may be good or bad depending on what your after. Same routine, wash with fresh water and blow dry and apply the appropriate primer straight away.

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woko said..
I like the idea of a blow dry but it would have to be dry air, like a hair drier or a paint stripper, then I would still use metho as it also removes oily contaminants. Though the hot air could help set epoxy.

I would not use metho, it has water in it. I would have thought acetone would be better. It removes all traces of everything.

My other hobby is repairing / restoring old mechanical wrist watches where water moisture is a huge no no..
Short of using specialised cleaners in Ultrasonic machines the fluid used for many decades by watchmakers to clean , degrease parts is Naptha (Shellite) sold by Bunnings ,Diggers brand.
After cleaning immediately blow dry . If a film left ,which should not be, wipe over with clean cloth. Some people use Isopropyl which is marginal as contains higher water %.

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keensailor said..
, am I doing something wrong, should I be cleaning the bare metal with something before priming. Maybe I am using crappy products?

Most cars these days are made with galvanized panels and zinc based primers so using phosphoric acid (will is what a lot of rust converters contain) will only make things worse as the acid reacts with the zinc and turns it into phosphate and hydrogen gas. Once the acid seeps into seams and cracks it will do even more damage as it removes any remaining zinc protection and any zinc based paint to use on top of it so you'll end up with even more rust then if you left it alone . Unless restoring a pre 90s classic forget turning rust into metal potions or acids and instead try to seal the rust using products like Penetrol or POR 15 then paint over that.


The way I'd fix it would be to remove all the crap from previous repair attempts with a wire buff or brush and scraper, sand it lightly if necessary and start again. Run the tip of a Stanley knife tip along the rusty seam to scrape any rust including paint covered rust. Then clean everything with metho a couple of times and use a hairdryer or electric heatgun over the seam to dry moisture trapped between the sheetmetals. Brush a few generous coats of Penetrol on the seam at 5-10 minutes intervals over the course of a few hours so it saturates the rust in between sheets. If is very rusty mix some turps in the first few coats of Penetrol so it goes in even deeper.
After 2-3 hours if you going to spray it with auto 2k primer clean the Penetrol from the surface before it fully cures then next day spray it. If you're just patching it with a paintbrush there is no need to wait, use turps based paint and mix some Penetrol in that, up to 50% in the first coat and no more then 5-10% in the last coat. The Penetrol will remove the paint brush marks and the job will look like it was done with the spray gun.

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AzureF305 said..
I'm having trouble with a little bit of rust in one of my cars.
Will the treatments listed above help me?

Good find.
Definitely restorable. Reckon it's a
1965 Pontiac GTO

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Bananabender said..

AzureF305 said..
I'm having trouble with a little bit of rust in one of my cars.
Will the treatments listed above help me?

Good find.
Definitely restorable. Reckon it's a
1965 Pontiac GTO

Apparently it's a 1964 Bonneville station wagon, although how you'd tell that I've no idea!

And here it is in all its glory after using a bit of rust converter and some elbow grease ,

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Harb said..
And here it is in all its glory after using a bit of rust converter and some elbow grease ,

So it will work eh? Excellent, I'll start right away!!