I was planning on returning the bondo, bondo makes a fibirglass infused filler, it was right next to what i bought, i watched some videos of it bieng used and i think it'll work, im going to see if they have the metal mesh reinforcing panel when i go as well. I treated the rust with locktite brand rust neutralizer. I have some heavy duty oil based rust oleum brush on paint, think that will work? Should paint it before the filler or after?tgreese wrote:Looks pretty bad. Fortunately it's hidden, so your repairs won't show much, but it's also a place that's going to be wet with debris and standing water a lot.
I have an air compressor, and I would buy a small media blaster and remove as much of the rust by spot-blasting as I could. https://www.harborfreight.com/21-oz-hop ... 95793.html Coal slag media is available at tractor Supply, $7 for 50#. Then I would flood the area with a tough rust-encapsulating paint. I like Aluthane. http://www.epoxyproducts.com/aluthane.html I would seal up all the bare steel and rusty areas with a heavy coating of this paint. If you want to use a chemical treatment, I have gotten good results from the Permatex product https://www.permatex.com/products/speci ... treatment/ - I would still top coat with Aluthane. There will be holes, and you'll need to seal them. Fiberglass would be ok, but not over bare or rusty steel. Bondo is the wrong thing to use for this, since it is polyester putty filled with talc and absorbs water if exposed to the air. If you want to use a putty, get one of the glass-fiber filled polyester putties like USC Duraglas http://www.uschem.com/index.cfm?page=pr ... tail&id=52
I understand, was just wanting to get this pretty much done this weekend. Don't really want to order anything.tgreese wrote:Make sure that you remove all the loose rust and treat any of the remaining rust so that it's completely sealed before you cover it with undercoating or whatever. Rust expands when it forms, pulling away from the substrate and exposing fresh material to the air and water. This is why they call it "body cancer" - it continues to progress unless you seal it completely from air (oxygen) and moisture. Most coatings do not stick to rusty surfaces, loose rust or not, but loose rusty surfaces are the worst. (One reason why I like Aluthane - it penetrates rust very effectively and sticks. Don't get it on your skin - it will have to wear off.)
2x, as Tim pointed out, rust is a very difficult cancer to fight. It is not a weekend project, you will have to repeat in a few months or a year.tgreese wrote:Make sure that you remove all the loose rust and treat any of the remaining rust so that it's completely sealed before you cover it with undercoating or whatever. Rust expands when it forms, pulling away from the substrate and exposing fresh material to the air and water. This is why they call it "body cancer" - it continues to progress unless you seal it completely from air (oxygen) and moisture. Most coatings do not stick to rusty surfaces, loose rust or not, but loose rusty surfaces are the worst. (One reason why I like Aluthane - it penetrates rust very effectively and sticks. Don't get it on your skin - it will have to wear off.)
I would guess that's not the problem so much, rather that the rust is a hydrate (Fe2O3·nH2O), and contains an excess of water. (This is the main reason why heavy, chunky rust is bad and thin, tightly bound rust is ok for some paints - less hydrate means less water). Your MCU coatings like POR-15, Rust Bullet, Aluthane and Eastwood scavenge moisture from the surface and bind it up in the urethane matrix. I'd suspect any polymer coating is going to seal pretty well to H20, but be a little bit permeable to O2, even when new. The MCUs work to enhance that seal by using an impermeable and overlapping pigment, like aluminum powder, or a metal oxide.letank wrote:tgreese wrote:... Metal will rust, even under painted areas because the paint or the clear coat become porous with age. ...