porschejim928

I have some rust in my battery box no doubt from a battery leaking at some point in its history . Structurally it is still real solid. Now I'm debating what all I should do to repair. I've used some baking soda and water and now I'm going to remove the rest of the rust. After that I'm not too sure what I should do. I was thinking maybe use fiber glass to repair. But I guess I could use sheet metal and JB weld to fix the holes maybe. Can't weld and don't think it is advisable to so near the gas tank. I've attached a pic. Would like to know how you would fix it.

Fogey1

That's crucial. Mine didn't have any holes when I cleaned it up ten years ago. Nor did I know then about rust converter.

If you're correct it's solid, the wire brush or wire wheel on a drill is the first step. I would use a rust converter next, then paint, then spray undercoat, then aluminum tape, then spray undercoat.

Be sure to clean up the bottom, i.e. outside, surface, too. Skip the aluminum tape but be generous with the spray undercoat.

Actually, you can probably skip the tape altogether if it's good and solid and well-sprayed, but rust converter and paint are important.

The spray undercoat can be further spread and smoothed with a disposable paint brush and a 60-100W shoplight left on and closed in the battery well speeds up the drying of the undercoat.

Be sure to use a vent hose with the new battery and be sure it's routed outside.

brealytrent

Mine wasn't structurally sound. Had a new one built by the local welder.

Tails

Wire brush and use "Rust Converter" - Phosphorus Acid and allow it to dry.

If the box is structural sound I would then coat the box internally with 'de-oderised fish oil' and every year when you undertake your electrical service as recommended by Wally (see his technical tips at 928 Specalists) and apply a coat of fish oil.

I have been spraying my battery box with fish oil now for 12 year with no corrosion.

STRIKEMASTER

Many years ago I had a '66 V.W. square back that I got dirt cheap. The battery box
was so rusted that the battery actually fell out on the ground while I was driving it!!! I ended up making a fiberglas box for it. Clean out all the rust, coat it with rust reducing paint and fiberglas it: 1 layer of 1oz. glass mat, a layer of 10oz. glass cloth, another layer of 1 or 2 oz mat and another layer of 10oz cloth. I used polyester resin to make my battery box because I was working for Hunter Marine at the time. Epoxy resin works just an good and stinks less. If there is a boat yard near you they should be able to hook you up with industrial quality materials to do the job. The lay up job will take about 2-4 hours to complete.

OTR18WHEELER

rust is cancer, for best long term results remove all rust to bare metal, A fine wire round cup brush for a drill would probably be the easiest to use. consentrate on the interior surface first. when rust is removed prime bare metal with a bare metal primer. for the external do the same. external surface will only need primer, and then a few good coats of undercoating.
If you need to patch the holes, fiberglas is a bitch for the novice.
perhaps consider a bottom inlay prefabbed to fit the bottom.

Fogey1

Phosphoric acid! That's what I was trying to remember.

I used it 6 years ago on a steel sculpture that lives outside on the patio. It turned the iron oxide (rust) into a black substance that not corroded since.

BUT, if you get all the way to shiny bare metal, the converter doesn't work. It needs the rust for the chemical reaction to work. Don't leave big flakes or anything, but don't go to bare metal. I did find, on the sculpture, that I could let the bare spots re-rust and then use the Phosphoric Acid converter.

osborm

Hi, Do a search on por15, hope it helps.

77tony

Spray or brush on, let sit overnight, clean with baking soda/water solution. Make sure you wear eye protection, rubber gloves and don't spill any on concrete. T http://www.ospho.com/directions.htm

porschejim928

Thanks for the suggestions guys. I cleaned it up with a wire brush and used some naval jelly. Right now I have the first coat of paint on the metal. Gonna coat it again then decide on how to fill the holes. I have some aluminum tape I'm going to try. If it seems to hold good I'll put a coat of undercoating over it and on the outside. I'll post a pic when I'm doine.

Brent

3M Rubberized Undercoating. Kind of sticky but still working.

240Z TwinTurbo

Sorry to bring back from the dead, but are the holes in the bottom of the battery box supposed to be there without being sealed? I noticed these on mine as well and thought it should have some type of plug sealing the hole. I did a search and could not find the answer.

wpgshark

Yes the 3 holes are suppose to be there to vent and drain the compartment. Only the front one has a grommet type cap which reduces the hole size.

928Collector

How do i remove this glue/lacquer(blue circled areas)?

davek9

First thing I would do is remove that blue vampire wire clip, they suck

As for removing the factory coating, mineral spirits or lacquer thinner should do it w/o harming the paint.