How should I treat this rust?

C4 Pazzo · 01-11-2007, 05:18 PM

I'm seeking input on how to treat some rust on the passenger door of my 1970T Targa. The first pic shows a nickel-sized spot just below and to the left of the door latch. It appears to be connected to one of the screws that holds the latch to the door. It does not go all the way through, but is trying to get there.

The second pic shows the inside, bottom front of the same door. I believe this rust resulted from the PO's failure to replace the rubber plug from the top of the door. This resulted in rain/wash water collecting inside the door. I do not know if the two spots are related (I don't see similar rust inside the door).

My question is, how should I address this rust? Should I apply the three-step POR15 treatment? Or do I need to reinforce the sheetmetal (particularly near the latch)? TIA for your comments.

scarceller · scarceller's Garage

Are the doors the only rust problem? and what is your goal? to just contain the damage or really get rid of it? Are you concidering painting the entire car soon? You need to tell us more.

I had a 75 911S that had issues like this, just the doors and front fenders where bad so I decided to buy used doors and fenders from an early 80s that where in perfect condition and had the entire car re-sprayed and after that it was perfect. Had it for 12yrs and no new rust showed up then I sold it.

MattAlpha · MattAlpha's Garage

Remove the screw and then majority of the surface rust with a wire brush and the surrounding paint until you're sure that you've got good (non-rusty) metal around the rust area.

POR sells a product called "Marine Clean" (I think that is the exact name, well its on their website). It reacts with the rust and turns the iron-oxide into another compound that no longer continues to rust out the metal. Use gloves when you're applying it. Let it sit for 10-20 minutes and then rise it off with water. Dry the area with a cloth and then let it air dry for about 15 minutes (longer if its cold). Once the area is completed dried paint it with an etching primer. Once that is cured paint it with a paint that is matched to the cover of your door.

Don't forget to have fun with it!
-Matt

C4 Pazzo · 01-11-2007, 07:39 PM

Driver's door is fine; just the passenger door has the problem. There are a couple of spots where the undercoating got scraped off that have some surface rust, but otherwise the car is pretty clean. My first goal is to contain the damage. I wasn't planning on repainting soon, but I might bite the bullet and do it. The current paint job is ok, but has some chipped spots that were badly touched up. I'm currently refurbishing the car, focusing on the mechanicals, but I feel like I need to do something soon about these two rust areas. I must admit I've been holding off on installing new weather seals while I decide about repainting the car.

C4 Pazzo · 01-12-2007, 07:30 AM

Thanks for the suggestions. I'll try MattAlpha's approach.

Keith Perry · 01-12-2007, 01:47 PM

Marine clean is POR 15's degreaser offering. It works well as a degreaser. I wash sails and convertible tops with it and it is amazing how clean they become. Matt is right, POR 15 is really good. Lately I've been reading here about Gibbs Brand Penetrating oil. I've ordered some to spray down my little collection of fans and shrouds. Supposed to make magnesium and aluminum look really good. The idea is this stuff really displaces moisture deep within the metal's pores, so I'm going to derust something around here by knocking the rust off, spaying with Gibbs Brand for a few days, washing with Marine Clean, a coat of Metal Etch Primer, 2 coats of POR 15, and then primer, paint, polish and wax.