Opinions sought on best epoxy primer please.

[steveo3002]

whizz over the scabs with a clean n strip disc then on with the blaster or rust gel

 

[Favguy]

yep so cleaner will be better , keep going till no brown pits then primer without it sitting about in the damp

I quite like the 1 pack epoxy rust converters for undersides...2 part epoxy primer is great if you can prep properly (ie blast) but with my imperfect prep when I've used it the adhesion hasn't been great!

...looks like you just want to touch up a couple areas and stop the rust progressing any further?

Have you had any long term success with rust converters then? I gave up on them years ago after finding they all seemed to fail after a very short period.

 

[Favguy]

Spotblasting will be perfect for those rusty spots and then a couple of coats of epoxy primer by brush before applying whatever top coat you want.

The below was done on the inner guard of a very rusty Alfa and didn't take that long.
The trick is get it close by whatever method you can (grinding, wire brush, sanding etc) and then give it a final going over with the spot blaster which gives you an ideal surface for primer.

View attachment 449999

I'd be surprised if there aren't other problems lurking beneath the rubber seal, but if you keep on top of it you should be ok.

All you can do is repair any issues as best you can (so you don't have to do them again) and deal with the next issue as soon as it arises.

Yeah, I really don't like that ****ty black coating, but it was put on when the van was almost new rather than more recently to hide existing rust, the only issues I've seen after extensive checking over are areas where the surface has been damaged by careless jacking, the wheels rubbing and some minor impact damage, so once those areas are rectified, it'll get a clear wax coating over the underside and regular inspection for any new issues. No winter use and proper garaging should see it outlast me hopefully lol!

 

[Favguy]

whizz over the scabs with a clean n strip disc then on with the blaster or rust gel

View attachment 450004

Hmm, I've not come across those, will give them a try, where do I find them?

 

[steveo3002]

i get mine on ebay and use them on a cordless die grinder , you can get other sizes for grinders /drill etc , they remove paint/coatings fast without too much damage to the good steel, and they last well too

 

[Pigeon_Droppings2]

you had any long term success with rust converters then?

I use the 1 pack aerosol converters...I'm pretty happy with them. I feel like it adds a layer of protection just in case the top coat fails.

That black underseal i think dries out over time and cracks and lets water in...but it's not visible until the rust takes hold. I prefer stuff that visibly ages so can be maintained.

 

[marlinspike]

I've used BH Hydrate 80 rust converter on pitted rust in hard to reach places. No rust has come through even after a few years, though this is in areas like the boot that don't get wet.

 

[richie00boy]

Rust converters would be pointless for the issues on this camper, using a proper acid the rust can be totally removed without too much bother and the repair will then be as good as new rather than sticking plaster.
I've found citric to work better than phosphoric on stuff like that, the trick is to keep it warm. I used kitchen roll pieces soaked in citric solution and kept wet with a hand sprayer they stick in place. Warmth achieved by a halogen floodlight pointing at the area.
If you were using Lechler you would be limited to citric as phosphoric will affect the zinc phosphate in the epoxy.
The rustbuster epoxy mastic you have is ideal for these repairs, it's a bit thicker than the Lechler and is designed to be brushed on.

 

[Favguy]

Rust converters would be pointless for the issues on this camper, using a proper acid the rust can be totally removed without too much bother and the repair will then be as good as new rather than sticking plaster.
I've found citric to work better than phosphoric on stuff like that, the trick is to keep it warm. I used kitchen roll pieces soaked in citric solution and kept wet with a hand sprayer they stick in place. Warmth achieved by a halogen floodlight pointing at the area.
If you were using Lechler you would be limited to citric as phosphoric will affect the zinc phosphate in the epoxy.
The rustbuster epoxy mastic you have is ideal for these repairs, it's a bit thicker than the Lechler and is designed to be brushed on.

Yeah, I've been working over the under arch areas again today, decided to just use my 81% phosphoric neat this time, soaked a sponge in some and dabbed it on over the area, gave it 5 mins, dabbed more on, then worked over the pitting with scotchbrite pad and a small fine hand wire brush. After a couple of sessions of this, all the pitting rust is out and it's all bright silver and utterly rust free. Wiped everything off whilst still wet, followed by a final light wipe on/off with very dilute phosphoric acid and let it dry for 1/2 an hour.

Question now is, do I leave the phosphated surface as it is for protection and paint over that?, or abrade first, removing it, prior to painting?

 

[ajlelectronics]

Question now is, do I leave the phosphated surface as it is for protection and paint over that?, or abrade first, removing it, prior to painting?

If you don't abrade it, your primer will fall off. The epoxy will provide far better protection than what is on there and is not acidic either.

 

[Morris]

I always scuff the phosphated surface up with a coarse scotchpad.
Not had any primer fall off to date. In fact it sticks very well and if attacked with a metallic objects the primer scratches but stays put.

 

[steveo3002]

Yeah, I've been working over the under arch areas again today, decided to just use my 81% phosphoric neat this time, soaked a sponge in some and dabbed it on over the area, gave it 5 mins, dabbed more on, then worked over the pitting with scotchbrite pad and a small fine hand wire brush. After a couple of sessions of this, all the pitting rust is out and it's all bright silver and utterly rust free. Wiped everything off whilst still wet, followed by a final light wipe on/off with very dilute phosphoric acid and let it dry for 1/2 an hour.

Question now is, do I leave the phosphated surface as it is for protection and paint over that?, or abrade first, removing it, prior to painting?

sounds more like it , where did you get the acid , sounds like i ought to own some

 

[Morris]

APC Pure

APC Pure is a leading chemical and reagent manufacturer

apcpure.com

 

[Morris]

I find that using phosphoric acid at high strength is counter productive, it is quite oily at high strength and is not as effective as you would expect. I used 30% for rust removal and 12% for the wash. Wipe very dry using clean paper wipes, allow to flash off the last of the moisture and scuff up ready for paint.

 

[steveo3002]

is this what jenolite is /was?

 

[Morris]

is this what jenolite is /was?

Yes, just for more money.

 

[barracuda816]

I find that using phosphoric acid at high strength is counter productive, it is quite oily at high strength and is not as effective as you would expect. I used 30% for rust removal and 12% for the wash. Wipe very dry using clean paper wipes, allow to flash off the last of the moisture and scuff up ready for paint.

Thanks for this. Interesting recommendation.

I have been looking at options for an upcoming resto that has a lot of surface rust and im always trying to improve my methods. Would a 12% phos wash still be enough to compromise the adhesion of the lechlar epoxy do you think? I want to find a way to stop the flash rust after surface prep and a weak phos wash may be perfect for that.

 

[Morris]

Thanks for this. Interesting recommendation.

I have been looking at options for an upcoming resto that has a lot of surface rust and im always trying to improve my methods. Would a 12% phos wash still be enough to compromise the adhesion of the lechlar epoxy do you think? I want to find a way to stop the flash rust after surface prep and a weak phos wash may be perfect for that.

I find that after a 12% wash bare steel can sit for weeks without flash rust. I really should do a test piece to see how long it will last.
As I said, I scuff up with a coarse Scotchpad before applying Lechlar epoxy and it's never given me any issues with adhesion.
I am not a professional so opinions may vary

 

[ajlelectronics]

Thanks for this. Interesting recommendation.

I have been looking at options for an upcoming resto that has a lot of surface rust and im always trying to improve my methods. Would a 12% phos wash still be enough to compromise the adhesion of the lechlar epoxy do you think? I want to find a way to stop the flash rust after surface prep and a weak phos wash may be perfect for that.

An immediate wash with slow panel wipe should be all that you need to stop it flash rusting. If you don't properly abrade the panel, the coat will likely fail at some point.

 

[barracuda816]

I think it's often a little too humid here and my work processes. I often blast areas (mainly underbody and engine bays), Blow them out with compressed air. Wash it down and blow dry again with clean dry compressed air. If I don't get it in primer PDQ then I get a little flash rust. Adhesion I agree is key (pun intended)