Primer for Rust-prone Spots?

[ammodram]

Guys -

I'm going to have a friend repaint the fenders from my Kubota L245DT.

The undersides of these fenders are really prone to rust, and they are getting hard to find replacements for. I want them to stay intact!

Is there a good rust-inhibiting primer I should have him use after he gets them cleaned up?

I was planning for the top coat to be the "old" color of Kubota OEM orange, but I don't know what to use on the bare metal first.

Thanks!
Matt

 

[Slacker]

I used "rubberized" undercoating on several jeep frames and they are looking great after 5 years. It's cheap spray bomb cans at the auto parts stores.

 

[ray66v]

Tractor Manufacturers are often guilty of using single step direct to metal paints, that do not protect metal well, leading to the situation you are experiencing.

I have tested every possible way of stopping corrosion repeatedly over the last 30 years in the Auto Body business.

There are many good primers avaliable today. However, they can be expensive.

A good primer will be able to self etch, (create a chemical bond), and have a strong high density, low porosity film. This film will protect the metal from moisture penetration and thus limit corrosion. If You Have a Sherwin Williams Automotive Store in your area I recommend NP75, (does everything including fill), although I am not sure if it comes in quarts.

Though some products out there are single component, (all in one can), and claim to be all the above, they are simply inferior. Only the 2 component primers are able to do everything well. Plan to spend in excess of $100 for a quart of primer and activator, at your local Auto Body supplier. They all make similar products, just make sure it is a direct to metal primer.

In lieu of that, you could probably do ok, after careful removal of rust in the affected areas, with a Rustoleum, or similar, primer, and some type of topcoat.

The rubberized undercoating from spray cans, mentioned in a previous post, is a cheap way to form a self adhering barrier, and is often used as such. However, I personally have not found this to be an effective way to really protect things. It is more suited as a way to hide corrosion. The barrier these products create, unlike professional undercoating, can be porous. This can lead to reoccourance, with the big problem now being the surface is covered with undercoating. Now you will have to remove the undercoating, (bigger mess), to treat the corrosion. NEVER paint over undercoating.

 

[swines]

I've had good results using Eastwood Company's two step process using the rust converter on rusted areas followed up by the rust encapsulator, and then final paint.

Eastwood Company: Search Results for rust

 

[ray66v]

I've had good results using Eastwood Company's two step process using the rust converter on rusted areas followed up by the rust encapsulator, and then final paint.

I have not used the Eastwood products, How long can you say it has worked for you? We tested similar products many years ago, on chain link fence posts, and found they did work, but, only about a year or so. I would think they have gotten better since then.

I have used a similar products to the fast etch they sell, it should work very well under most basic primers to give a good bond.

Both could be a good solution for rust you can't get to.

Since you can't always get a quality finish painting over some of these products, they should be tested, through trials to determine if they will cause shrinking or swelling with the particular top coats you want to use. Unless that is not an issue.

 

[RalphVa]

I'd use Rustoleum's Rust Reformer or NAPA's Trustan (think this is what it's called). These react with iron oxide (rust) and convert it chemically to a hard, black iron sulfide.

Ralph

 

[dqdave1]

You may want to try POR 15; look on ebay. people swear by this stuff.

 

[john_bud]

Dupont Corlar 2.1 PR. It's a 2 stage industrial primer and is hard as nails. It is a pure pain to work with if you are using garage equipment, but if your buddy has pro equipment, it's not too bad. The finish will look "hammered" and not flow out smooth, but for the underside - who cares?

PPG has an equivalent product.

Both REQUIRE supplied air respirators.

jb

 

[Skyco]

I like the cold galvanizing zinc rich paint for things that may rust. That stuff works great and even if chipped it will sacrifice around the chip so the chipped area still doesn't rust.

RustOleum.com

The stuff is real bad about clogging up the spray nozzle after use so be sure to do the upside down spray until just gas routine.

 

[sunspot]

I remember reading about primers on YT. There was a guy there that sweared by using a Phosphoric acid product. He said it blackened the metal sorta like gun bluing.
Anyone know of any products like that?

 

[swines]

We tested similar products many years ago, on chain link fence posts, and found they did work, but, only about a year or so. I would think they have gotten better since then.[have not used the Eastwood products, How long can you say it has worked for you?

Funny you should mention fence posts. I have about 1500 feet of pipe fence around part of my property. It's made from old drilling pipe, and some of it is rusting through the paint put on by the original installer.

To repair those areas, I've been wire brushing the heavily rusted areas to knock off the rust flakes, and then use the Eastwood products. I've used the 2-part rust converter previous to the current product - and no rust on areas repaired 5 years ago.

I've been using the Eastwood rust encapsulator as the primer on tractor implements for about 3 years. I clean the implements with abrasive wheels to knock down the rust and feather out chips in the existing paint, and then prime with the rust encapsulator. The implements primed with the rust encapsulator seem to keep their paint better than the ones primed with zinc chromate primer.

 

[alvanko]

Phosphoric acid is just that. Acid. It will treat the metal and get microscopic rust that is not scene. It is not a primer. If you used the acid, it would need to be neutralized with water, dried as quickly as possible and primed as soon as possible. I used to use it when I owed a body shop but, I would rather sandblast and prime, then use the acid. Seemed silly to clean the rust then rinse with water. Always seemed to get a surface rust imediately after rinse. IMHO sandblast and epoxy prime is the best, followed by "quality" top coat. All depends on how much you want to spend and how good of a job your looking for.
I suppose anything is better then nothing.

 

[ray66v]

I had the same misgivings about using water on steel, then I went to the mill one day, and saw the first thing they do to a brand new piece of steel was spray water on it!? There are ways to etch the steel without water. An etch is very important before primer unless you are using a self etching primer, Most epoxy primers today are not self etching, and therefore, not really meant for direct to metal use. The paint Companies tend to allow this to an extent, in their warranty programs. However, it is cutting corners. using an etch before primer is the best, and cheapest way to prevent future corrosion.

Swines, thank you for the review on the Eastwood products. If you are grinding the metal prior to applying a coating, may I suggest you grind with as fine a disc as possible. Grinder marks that are very deep are prone to not filling completely, and the subsequent voids can be a source of future corrosion. I would avoid anything in the way of zinc chromate primer, these products were reformulated many years ago, because of EPA regulations, this left them impotent.

The best primers today are not soluble, meaning they will not soften up with thinner, and that leaves out anything that does not requiring any kind of hardener/activator.

 

[john_bud]

I remember reading about primers on YT. There was a guy there that sweared by using a Phosphoric acid product. He said it blackened the metal sorta like gun bluing.
Anyone know of any products like that?

One product is "Must for Rust". It converts surface rust to iron phosphate that is naturally rust resistant. No rinse is needed and you can prime / paint as much as a year later. (I have not done that) I have sprayed bare angle iron on my trailer where the paint chipped off and after a year it still looks rust free there. (I do have to check it now that spring is here and the trailer is out of the snowbank.)

There are other products that do the same. Picklex (sp?) is one.

 

[sunspot]

Thanks to all that contributed to this thread. I've learned a lot about primers and I have it bookmarked.

 

[ammodram]

Thanks for the info, everyone. I've taken the fenders off and delivered to the painter. I'm not yet sure what primer he's going to use. I know he will definitely sandblast the rust off first. When I talk to him next, I will find out which product he is planning to use, and then let you all know how it works out.

-Matt

 

[patrick_g]

I painted (brushed on) lightly rusted steel columns (4x4 steel tubing) with Rustoleum's direct to metal primerless rust converting hammertone product (got it at Lowe's) over 4 years ago and it still looks like new and is on the south side exposed to weather and sun. I have also sprayed the product with good results.

I previously used a water based primer (by Rustoleum I think) on rusty metal exposed to salt water in the bilge of a sailboat. This went on in a sort of cream colored (maybe a slight green tinge) and when dried was dark purple to black (rust to other iron compound causes color change.) This stuff survived repeated and at times continuous wetting with salt water for several years and when a marine surveyor inspected the boat for insurance purposes he was totally amazed at how well preserved the painted metal and nuts and bolts holding on the keel were.

Pat

 

[horse7]

I like the cold galvanizing zinc rich paint for things that may rust. That stuff works great and even if chipped it will sacrifice around the chip so the chipped area still doesn't rust.

RustOleum.com

The stuff is real bad about clogging up the spray nozzle after use so be sure to do the upside down spray until just gas routine.

I tried this many years ago on a bumper, spraying one stripe (about 3" wide) of the "cold galvanizing", one of cheapest gray primer, and one stripe of the rust converter. Surface prep of sand blasting (Black Beauty medium (slag)) followed by acetone wash to remove oil.

The cold galv did a little better, but was very disappointing considering the hype (and cost).

Coated one fuel tank with POR15 and that seemed to work well, but the vehicle was deadlined too shortly afterwards so there aren't long term results. (and I accidentally left 1/2 qt of POR15 in the fridge when I moved from one place to another , someone got better paint than they expected!)

I don't have a rusty car on the road now; I am ready to electro galvanize rust spots when they show up on my current truck-- zinc acetate with sacrificial electrodes of stripped pennies. Not ideal, but probably good enough for proof of concept. My hypothesis being that the spray on did not work due to the insulation of the binder between the zinc particles and the base iron in the spray on. So, by electrogalvanizing, there should be good electrical connection.

[another possibility would be terne coating, but due to the even relatively mild hazards I'd prefer to avoid that one]

 

[patrick_g]

I don't have a rusty car on the road now; I am ready to electro galvanize rust spots when they show up on my current truck-- zinc acetate with sacrificial electrodes of stripped pennies. Not ideal, but probably good enough for proof of concept.
[another possibility would be terne coating, but due to the even relatively mild hazards I'd prefer to avoid that one]

First time anyone has referred to terne or terneplate around me in 20 years. Marine grade fuel tanks used to sometimes get thick terneplate coatings.

Clever trick with your electroplating. Used to be standard flashlight batteries were a good source of zinc as the cup was zinc. I used a few zinc Mason jar lids in my time too, raiding trash heaps to find them as they were already out of fashion when I was in grade school.

To reduce rusting of "stainless" steel (especially the stuff on cheap yachts out of Hong King and Taiwan) I came up with an idea of reverse plating the iron from the surface to leave higher concentrations of chrome and nickel.

Pat