Rust repair

[GSpreeman]

I have a few 1/4 inch spots of rust at the base of my doors. I've stripped the paint around the rust to make sure it doesn't go any farther. How do I repair these holes?

[Formerly Steve Wilkinson]

I'm not sure what you mean by "the base of the doors"--The sills under where the doors close? The bottom of the door's exterior panel?--but no matter what anybody says about a variety of rust preventive measures such as POR-15, which is excellent, and which I've used--the bottom line is that "Rust Never Sleeps." You can cover up rust, you can paint over it, you can sand it off until the sun shines...but ultimately, what you have is a chemical process that has begun and won't quit. So you can slow it down--indeed you can slow it down a lot--but the only way to "stop" it is to torch out the metal that is rusting and weld in some good steel.

Oh, and "stripping the paint to make sure the rust doesn't go any farther" is not going to achieve that purpose. The rust is going to go where it wants to go, it's just that now you can watch it.

Bottom line is that there are a variety of temporary cures, and the absolute very best of them just might cure the problem liong enough that you no longer care--the care is used up, or sold or whatever--but the only permanent cure for rust is to excise it.

Stephan

[GSpreeman]

The spots are on the bottom of the exterior of the door (clogged drainage holes, water sitting inside...). So, if I can trim out the rust leaving a hole about 1/2 inch in diameter can I then use a MIG welder to weld in a little piece? The reason I ask is I'm getting a MIG in a few weeks.

[Formerly Steve Wilkinson]

I would think that the first thing to do would be to correct whatever caused the problem in the first place--whatever is clogged, not draining, trapping moisture, etc.. Then what you'd need to do is figure out where there is lots of rust that hasn't yet eaten its way through, and that will simply be sitting there waiting to corrode again. As I said, Rust Never Sleeps. It sounds like what you have is a situation where simply removing the external signs of rust and replacing them with fresh metal will simply give the existing situation more new steel to eat, no matter how nicely you weld new stuff in.

It might well be that if you really want to make a permanant repair, you need to cleanly remove a strip of metal, clean everything out inside it, and replace it with good steel. I doubt that plugging little holes and trapping the original problem inside them will last for long.

Stephan

[RickM]

Like Stephan says....fix the original problem and replace with quality sheet metal. I'd think there is residual rust in the area as well.

You may want to consider using galvanized steel to fashion a replacement with. Be careful though as when welding galvanized metal toxic fumes result. Do in a well ventilated area with a mask.

Clean the welded and surrounding area well and consider spraying with a zinc based primer. Then use POR 15 to coat the affected and newly patched area. Make sure you replicate any drainage holes/vents that were there originally.