Rust converter questions

[Mavawreck]

I've coated a few of my trouble spots with rust converter, I'm going to coat the panels with 2k primer but I haven't seen anything about whether sanding is necessary or would make the rust converter ineffective. Thoughts? My gut tells me to hit it with 320 first.

[Rich88]

Originally Posted by Mavawreck

I've coated a few of my trouble spots with rust converter, I'm going to coat the panels with 2k primer but I haven't seen anything about whether sanding is necessary or would make the rust converter ineffective. Thoughts? My gut tells me to hit it with 320 first.

Look carefully at my avatar. This is what you get two years after NOT sandblasting every possible rust cootie off before coating with converter and painting. I only sanded heavily and used a rotary wire brush. My gut now tells me to sandblast every speck outa there, coat with bondo, smooth sand, and then paint.

[Mavawreck]

I hit it with a flapper wheel and then converter, then covering with epoxy primer, then filler, then primer, then base coat, then clear.

[catch2otwo]

As far as I know rust converter "encapsulates" the rust cutting off the air supply stopping the process. If you were to sand it after coating, I would assume your going to break that barrier exposing the rust to air again.

[tgreese]

Depends on the product. A rust converter only converts the rust from one form of iron oxide (red rust, aka hematite) to another form of iron oxide (black oxide, aka magnetite). This is the same black oxide that you see on some tools, and on nuts and bolts. Some rust converters make a different compound from the red rust - but they still convert the oxygenation state of the red rust to a more benign compound.

Red rust is bad becasue it expands as it forms, pulling away from the substrate and exposing unrusted metal to the elements. Thus once started, it keeps going on its own.

None of the rust converters are intended as a coating, AFAIK. You still need to top coat them with something.

There are also rust encapsulating paints that seal the rust from air and moisture and thus stop the rusting. These are mostly moisture cured urethanes, that pull moisture from the substrate as they cure and prevent rusting. POR-15, Rust Bullet, Eastwood Rust Encapsulator are all this type of product.

I believe you cannot use 2K primer over rust converter. You can shoot 2K epoxy primer on bright metal, or use an etch primer and cover with a 2K primer. Neither approach is ok over anything but bright metal or filler, AFAIK.

[Mavawreck]

Originally Posted by catch2otwo

As far as I know rust converter "encapsulates" the rust cutting off the air supply stopping the process. If you were to sand it after coating, I would assume your going to break that barrier exposing the rust to air again.

I'm not too informed in this area, but that was one of my concerns as well. On the other hand the converter is not terribly smooth and according to what Tgreese just said it needs to be sanded anyways for the primer to stick.

[CJ5]

I am using Eastwoods Rust encapsulator and have talked to them about this. Thier product requies topcoating with 24 hours or it will have to be scuffed.

Now the rust converter is a different story and product all together and I cannot give any advise on that.

[tgreese]

Please note rust converters are not paints; instead, a chemical treatment, like Naval Jelly. If you're using a rust paint, consult the manufacturer for what top coats you can use, and what window you have for top coating.

Sanding metal treated with rust convertor does not make much sense. If I were going to sand, I'd sand off the loose rust before treatment. The converter does not 'set' like a paint, so there's no issue with roughening the surface.

[djongeward]

Hmmm, the "Rust Converter's" I've used, and successfully, I would say, convert rust to a "primer" like finish, that accepts paint, or primer, and sands like primer. I've sanded treated areas and primed, or left it as is and primed, or painted directly over it. I've done this when I lived on the coast and had some salt exposure via surfing, and hadn't had any continuing rust issues to treated areas. As I now live in a very dry desert, those areas have continued to hold up and I suspect it is because of the dry environment.

I have had small issues with areas I thought I had treated but did not reach everything, like under paint near a treated spot. I have had a spot bubble up with rust near a spot treatment and so I have learned to be more through. You can't expect miracles. I have had really good rusults with treating frame areas on old vehicles and trailers. Treat, then spray with black. You have to get down into the rust using picks, wire brushes, or wheels, depending on how wide spread the issue is. I've found it is a good safeguard to convert rust you can't get at, like a weld spots small holes, then paint.

The best approach is complete sanding to bare shiny metal, but this is inconvienent or not practical in many situations.

I am really glad I do not live in areas where you have constant exposure to water and salt like most of you do.

[Mavawreck]

I sanded all the areas with a flapper wheel before I treated them. I've noticed over the past 48 hrs they've gotten darker (the metal has turned black and converter has firmed up). I cannot see where the primer would adhere very well to unsanded converter but it should remain down in the pores and the pitting where I cannot/don't want to get to.