What’s the best way to treat this rust on the floorboard?

[A930Rocket]

As part of my wooden floorboard repair, I need to take care of this rusty area. Obviously, I need to remove the stud and install something else, but what’s the best way to treat the rust?

I was going to start with a wire wheel but don’t think I want to sand it down, thinning the metal.

Then apply a rust inhibitor.

Thoughts?

[javadog]

That looks pretty superficial. Hit it with some phosphoric acid and a nylon scrub brush and then see what you really have when you remove the surface contamination. I think most of that will go away.

Take a look at the underside of that area, too.

[Zeke]

I'm with java and once treated, neutralize and go ahead with a polyurethane coating to seal off the metal preventing moisture and O2 from getting to it. Pretty standard routine.

[A930Rocket]

Thanks guys. I wire wheeled it, cut the stud down, then applied a coat of phosphoric acid.

Question….do I leave it as it is or do I neutralize it with water? The directions on the pre-diluted container, don’t mention neutralizing it.

[javadog]

IIRC, you can just let Ospho dry for a few days and walk away. If you're worried about it, wait several days and hit it with a weak solution of baking soda and water. Get that ALL (baking soda residue) off of it before painting.

[A930Rocket]

Roger that!

[Bill Douglas]

930, I've had very good results with Brunox. It's a phosphoric acid type product but is with a (sort of) epoxy base. So it keeps moisture and oxygen out as well as doing the rust conversion. I've been using it for a couple of years now and happy with it. And it can go over the top of what you have already done.

[A930Rocket]

Thanks, Bill.

I’ll look it up.

[Zeke]

I've had 2 kinds of phosphoric acid from the paint store. One left a bit of a film and I felt it must be rinsed. The other not at all. And I have read that you can leave the acid and paint right over it.

So with mixed info, I can't be sure, but I'd tend to rinse it and maybe not with baking soda after all. That is important with some acid treatments.

FWIW, the Jasco brand is what left a film while Krud Kutter brand "The Must for Rust" has always been the best. Hard to find and not to be confused with the Krud Kutter cleaner.

[A930Rocket]

I’ll take another look at the directions and check how dry the floorboard is after treatment.

From what I recall, it said it could be painted after 24 hours.

[Bob Kontak]

I searched long for a procedure before painting.

Wipe or brush Ospho on after removal of all but pits as you have done. Walk away for a day. Put more Ospho on to "loosen" up the dried acid the next day. Brush/agitate and flush with water (Javadog's baking soda water mix should work).

It will immediately flash rust. It's fine to put an epoxy primer on the flash rust. POR15 could be applied once dried for your case. I was painting the hood of a truck.

[A930Rocket]

Got home too late to do anything today. It’s on my to-do list tomorrow. Thanks, Bob.