Using JBWeld as one would use POR15 or Rust Bullet

[Nigel Tufnel]

All-

I had to remove the battery from the trunk of my car (German) to do something or other last spring, and was horrified to find a bit of surface rust on one of the weird plughole-shaped metal divit things underneath the battery tray (BMW E46). Those things are strange- they look like body plugs but they’re not, they’re actually part of the sheetmetal. I wirewheeled the rust off, and I *think* I remember using some of the Naval Jelly I have sitting on the shelf, then acetoned it then since I didn’t have any Rust Bullet on hand, I improvised with some good old JB Weld. My logic was deprive the area of oxygen, and the rust will be effectively stopped. It’s about the size of a half dollar. There is no corrosion on the underside of the car at that location. No idea how it started either.

Will JB Weld work like POR or Rust Bullet in this instance or do I have to grind it off and do it right with the proper stuff. I panicked because rust really scares the hell out of me. It’s been keeping me up at night.

Thanks

Topic

[James O’Hara]

As long as you made sure you pushed it down against the steel there should be little chance it will rust. The rust is probably from the battery and air condensation or the battery just venting as normal and it not having a vent line down and out of the car. So it went to the lowest spot and pooled which happens to be your battery tray.

[Thomas Byrd]

Sounds like you probably have it licked pretty good. If it starts to come back however just wire wheel it off again and try a little 2-part primer. Surface rust usually doesn’t really need something that drastic. You could use POR15 and then primer too. Keeping the air off of it as you mentioned is the goal with any of these solutions.

[Brian]

JB weld is not a good idea. It becomes pourus after a time. I had a customer bring me a car he attempted doing a full resto on, but got tired and frustrated so in it came. He thought regular body filler was too inexpensive to be any good, so he thought he was being car repair Superman by using JB weld in place of body filler all over the car. As I started to chip and grind it away, chunks fell off and there was rust restarting under it.
Por 15 is good stuff, but so is a little basic body work. This is an area that is tucked away, so you don’t have to make it look perfect. That gives a bit of room to learn without worrying about the look of it afterwards.
Grind and chip away that JB weld. When our down to bare metal, spray SEALING primer in bother sides. are there holes where the rust was? Fill them with something worthy, like 3m structural adhesives like the kind used to glue vettes together. Spray sealing primer on that again. Paint if you like, and I would. Any kind if paint, then clear coat it with UV resistant clear coat.

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