Rust Spot Removal Question
 

Below is a picture of a spot that the undercoating was scraped off. The car developed some surface rust and I have done a bit of work to remove it. I used some liquid rust remover and have sanded and scraped too. I looks far better now but any further improvements are going pretty slow. When i sand there is almost no noticeable rust coming off at this point. However, I suspect that there is still rust there on the blackish spots you can see in the pic. Should I keep scraping and sanding before I repaint and re-undercoat this spot or am I good now?

Thanks.http://forums.pelicanparts.com/uploa...1148053910.jpg

Looks pretty clean. Treat with a etch primer (wash or paint) and then top coat. Follow with some more undercoating (Wurth SKS is a good match) and you are done.

Good job preserving another early car. btw, the black deposits are likely a result of your "liquid rust remover." I suspect it was phosphoric acid based and those are phosphat residues.

Thanks. The liquid rust remover is phosphoric acid and sodium nitrate. I am going to get a needle or something small into one of those deposits and see if any rusty looking residue comes out but given sanding is coming clean I am hopeful its good to go.

POR-15 metal prep then POR paint on top will do it.

POR-15 is a product used to encapsulate rust. I may recommend that product. www.por15.com

In my opinion, you could pre-treat and apply and be done with it, no picking with needles. Why not fill the hole while you are doing it, too? Maybe some 2 part epoxy or jb weld putty?

Doug

The hole is for a little rubber plug. There are a few of these on the bottom of the car. not sure what they are for but I planned on putting the plug back in once its painted and then undercoat the plug and treated spot. The other rubber plugs appear to have undercoat on them so thats why undercoat after the plug is in rather than before.

Since you already did the phosphoirce acid etch, I'd just paint it over with POR-15 and call it good.

Thanks everyone.