Need some opinions here. Crawled under my car today and found that the A-Arms, cross member and surrounding area were covered in surface rust. Nothing serious and no rot...for now.

I'm looking for a quick and effective approach. I don't have the time to be pulling pieces off the car to wire wheel and paint them, and it looks like POR-15 would be more trouble than it was worth to slap on down there. I just want a product that can be applied and protect the typical unsightly surface rust from turning into a real problem.

Of course the first thing I was thinking about was heavy duty undercoating, but what about that stuff that can be bought that supposedly turns rust into "black primer". What if I sprayed the rust with the inhibitor THEN covered it in undercoating?

 

I would just spray it with undercoating.

 

I would use a wire brush and get any loose scale off first. Then spray a rust converter on. You can find the stuff that turns it into black primer at just about any auto parts store. Then I would spray the undercoat on.

 

I would wire brush it and us POR-15. You may think its a waste but its really the best way. Undercoating tends to hold in moisture so it could make the rust worse...

 

I didn't say POR-15 was a waste. POR-15 is a royal bitch to apply just about anywhere and the fact you have to use a paint brush makes it that much worse.

 

Ok well i meant i think it would prove to be worth the trouble for you to apply it now. Ive had some really good experiences with it... But i do agree that its not the easiest to use

 

Some of POR-15's competitors, and maybe POR-15 itelf, come in spray cans. Works fine, I've used it. Too lazy to get up and go out and see what brand it was that I used though, might have been Bondo or one of the paint co brands.

You still need to knock off the loose scale as much as possible.

 

I used POR15 on my truck frame that was brown from surface rust four years ago, still black today and holding up well, the truck has spent it's life in Michigan.

 

i would do this, the rust converter is called "ospho"

 

That is the absolute worst thing you could ever do if you have rust forming. The elderly lady who owned my Camaro before me did just that, and now I have no right rear wheel well, several areas of advanced rust under the car, paint bubbling up with rust creeping in under it, ect., ect., ect. and no way to fix it anytime soon due to a perpetual lack of money because of college for the last 6yrs.

 

Yes, ospho, or if you can get it just plain Phosphoric acid which is the primary component of ospho. Tannic acid will do the same thing. Look for products with either of these as the main ingredient. They are sold as rust converters or prep and primes.

Products like ospho turn iron oxide into iron phosphate which will not rust anymore. Knock the loose stuff off and just brush it on or spray it on out of an old spray bottle. Easiest thing would be to just pressure wash the areas in question and apply as needed.

 

Truck Bed Liner rattle cans I think are nearly the same to por15 just different places its used...but ive heard of truck bed liner being used on the chassis before for rust protection.

 

One of my favorite converters is Rust-Oleum Rust Reformer (can get it at WalMart), it dries a nice satin black.

 

FWIW, POR15 can be sprayed. Now unless you have access to a lift, spraying it may be a bit difficult

This is how I plan to apply POR 15 to my under body once I prep it. we ll see how easy this might be with the vehicle on stands.

From Application instructions on their website...

SPRAY APPLICATION Use 30-35 lbs (206-250 kpa) pressure for normal
gloss. Reduce pressure for lower gloss 20-25 lbs (140-170 kpa). Thin
only with POR-15 Solvent, if necessary. If topcoat to be done at later
date, apply very light dust coat of primer over tacky POR-15 and let dry.
Full priming and finishing can then be done later. Use POR-15 Solvent
or lacquer thinner for cleanup, which must be done before POR-15 dries;

 

bedliner is good at protecting from future rust, but does not solve or cure current rust (like por 15). you will want to prep the area first with a rust converter before going this route or you could end up making things worse

 

Scrape scale then use the POR 15 kit that's what I do and I have good luck. If it is a small area get their starter kit. Comes with EVERYTHING. about 20 bucks.