rusting through bondo

[Sammy D]

hey guys, so I had the typical rear quarter panel rust on my 95 eg, and decided to sand it down, then grind it down, then sand it more, then fill it with bondo, and then prime it gray. this was all about a month ago.

well, i'm not really sure how it happened, but the whole area that i'd ground and filled with bondo has turned from a gray to a brownish/gray around the edge, and i fear that it's begun to rust again! what did i do wrong? did i skip a step? i sanded it down and put another coat of primer on, as well as a clear coat just to try to seal it up, but i fear it may be coming back. any and all help would be appreciated.

(i've been using only rustoleum automotive spray products if it makes a difference)

 

[HeX]

You shouldve sealed the metal before adding Bondo. However, if there is significant rust underneath the sheetmetal then its likely the rust has continued to eat away the metal beneath and around the Bondo area.

 

[R3dline]

you can do one or the other.

cut said quarter out, put in new

or

knock you bondo out, sand the rust, and use some etching primer, which will kill the rust (sometimes) and redo body work,

id just put a new quarter in.

 

[yevangelis]

bondo absorbs water so it sounds like it got wet. Rust is like bacteria, by the time you SEE it, it's already well established at the micro level.

 

[mymmeryloss]

Primer isnt water proof either. U need to seal and paint it to prevent rust

 

[95Civic Dx]

Use duraglas!!!

http://www.uschem.com/products/docs/TDS_Duraglas.pdf

 

[Eg Civic Hatch]

Sand it all out, buy a mini sand blaster from your auto store should only be 30-50$ and some garnet "purple sand blasting material" Only go lightly so you don't warp it and keep going until you see no specs of rust make sure there is nothing behind it either, then prime with 2k epoxy urethane, then bog over that then prime then paint. It's what i would do because taking out a rear quarter panel costs a fair amount of money