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General => General Discussion => Topic started by: KeithB on May 11, 2016, 04:27:24 PM

Title: Painting over rust
Post by: KeithB on May 11, 2016, 04:27:24 PM
After two years, my Chinese camper trailer is starting to rust badly.
I have taken a test section, power brushed it and painted on some phosphoric rust converter.
I was going to put some cold gal over it, then prime and top coat. But the cold gal can says not to paint over any area that has had any phosphoric or other acid treatment.
The cold gal paint company lines are all engaged so I wonder if anyone can advise.
Keith
Title: Re: Painting over rust
Post by: muzza01 on May 11, 2016, 05:15:16 PM
I would just get a wire brush wheel on an angle grinder to clean up the rust. Brush on cold gal, leave for a week or so, prime and paint.  I presume it's underneath the CT so if unseen, just leave it in cold gal.  Your $$ will go a lot further if you buy a tin of brush able rather than pressure pack spray of cold gal.

Rust converter is great stuff but it uses an acidic compound that a lot of paints don't like. There are some that primer can be directly applied to.  How bad is the rust? Is it surface rust or ulcers.
Title: Re: Painting over rust
Post by: KeithB on May 11, 2016, 05:18:15 PM
It's a bit of both. Some paint damage with rust showing through. Some peeling paint with light rust underneath. Some heavy rust that won't come off with a power wire brush. Can't get in with an angle grinder. Hence the cold gal.
Keith
Title: Re: Painting over rust
Post by: edz on May 11, 2016, 05:48:42 PM
Diesel / sump oil mix , liberal coating by low preasure spray or brush and then a drive down dusty road for   underneath .Messy yes and will smell for a little while on a hot day, but will soak into the rusted areas and seal them .. recoat 12 monthly or more often  if dragged though lots of wet weather ..The mix gets into the grain of the steel and seals it .
Just be aware of closed sections of chassis could contain fumes if you intend welding at a later date .
Title: Re: Painting over rust
Post by: GBC on May 11, 2016, 06:07:25 PM
Penetrol in spray tins. Just follow the instructions and then paint over. If you don't care how it looks, the above will do, or we use lanolin in low pressure sprayers.
Title: Re: Painting over rust
Post by: Streetkid on May 11, 2016, 07:34:32 PM
Penetrol is pretty good stuff, I have found you need a few coats to make it do what it says but a little bit of this stuff goes a long way and there is no need to prime afterwards.
Title: Re: Painting over rust
Post by: KeithB on May 11, 2016, 09:46:45 PM
Just went onto the Penetrol website and it really looks the businenss. Bunnings has it. Thanks for the tip.
Keith
Title: Re: Painting over rust
Post by: Snow on May 11, 2016, 10:17:28 PM
PPC Por15 Rust preventatve rust paint system. Not cheap but is the ducks guts stuff.

www.ppcco.com.au (http://www.ppcco.com.au)

 :cheers:
Title: Re: Painting over rust
Post by: Aaron Schubert on May 12, 2016, 07:56:02 AM
You should always paint over cold gal - its porous and will rust through very quickly in the elements

Aaron
Title: Re: Painting over rust
Post by: shanegtr on May 12, 2016, 09:33:55 AM
PPC Por15 Rust preventatve rust paint system. Not cheap but is the ducks guts stuff.

www.ppcco.com.au (http://www.ppcco.com.au)

 :cheers:

Don't use it anywhere that's prone to stone impacts when on gravel roads. It will just chip off and it's expensive paint so you effort will be wasted. Any other areas it will be fine
Title: Re: Painting over rust
Post by: Footy Shorts Shane on May 12, 2016, 10:44:07 AM
Did it get a white, chalky, powdery finish after the converter was applied?
Title: Re: Painting over rust
Post by: JSKM on May 12, 2016, 10:58:41 AM
From experience )I am a  Project Manager of a Shipyard) you must do 1 thing before any painting.

Stop the rust.

Yes that sounds silly but you would be amazed at how many people give it a quick brush with a wire brush and just paint it.

How I would do it based on what we do here.

Clean up the scale and hit it with rust converter and let it oxidise over. If you get a good finish (mechanically prepped) rather than use rust converter, prime with a good etch primer. Note: Weld seems and joins are very hard to get a good sub straight finish when rust has been present, using a rust converter allows it to penetrate in areas that you can't clean-up by mech prepping.

Regardless of what option you use, follow the directions of the product you are using and paint over them as required.

Cold Gal is not the best option on bare metal that has rust pitting or has had corrosion on it as Cold Gal is a soft finishing paint and doesn't bond the best (not like an etch primer).

I am sure there will be other options put forward, but that's how we do it on ships and the salt water environment.

Cheers & Beers,

Joe
Title: Re: Painting over rust
Post by: Ashez on May 23, 2016, 04:06:25 PM
Another vote for penetrol - it's amazing stuff
Title: Re: Painting over rust
Post by: slydar on May 23, 2016, 06:17:51 PM
 yep, penetrol here too thanks to my middle stepson - but then he also soaks every car he buys in lanasol as well (and his workboots...) while I always use the etch primer on the aluminium boat
Title: Re: Painting over rust
Post by: KeithB on May 23, 2016, 06:55:17 PM
I have been using the Penetrol for the past couple of weeks on the trailer and on various rusty bits around the house. It's good stuff all right.
Title: Re: Painting over rust
Post by: BillC on May 23, 2016, 06:59:30 PM
Highly highly recommend penetrol

Had a trailer at work which I de rusted yearly. Tried everything for about six years. Then tried penetrol, surprisingly followed the directions on the tin.

That was years ago now and haven't touched it since. I wouldn't waste time with anything else

Bill
Title: Re: Painting over rust
Post by: MADCOW on May 24, 2016, 10:56:53 AM
Mate get some "Ferronite". It will stop rust dead in it's tracks and will turn it black. We use it at work in some pretty extreme environments and works a treat

http://boatcraft.com.au/Shop/index.php?main_page=index&cPath=5_53 (http://boatcraft.com.au/Shop/index.php?main_page=index&cPath=5_53)
Title: Re: Painting over rust
Post by: green troll on May 24, 2016, 04:55:54 PM
X2 on ferronite but watch where it runs as it will stain anything else.