Rust Encapsulators

I've been doing a lot of research on rust encapsulators in the last week, that's what products like POR-15, Rust Bullet, Zero Rust and Rust Doctor are. On the HAMB board there are quite few threads about them. One post mentioned that POR-15 started as marine floor paint. The person mentioned you can buy the marine floor paint for about 1/2 the cost of the paints marketed to the old car hobby.

I called a few industrial paint distributors to see if they carried specific marine floor paint. I described what I was looking for to one paint dealer and he said it sounded like I was looking for epoxy mastic. I searched the internet for "epoxy mastic" and found numerous posts and a few places that sold the product. Two products made by PPG and Rustoleum could be bought at local distributors including my local hardware store.

When you go to the PPG and Rustoleum web sites their descriptions of their products are exactly like the above mentioned rust encapsulators descriptions of their products. They are both made to penetrate and seal blasted or solid rusty metal. They need a surface that they can grab on to. They can are applied directly over solid rusty metal. They both can be used as a primer or as single type coating. Like all the rust encapsulator products their finishes turn chalky if left exposed to UV rays. One major drawback to the POR-15 product is it's not easy to paint over. You have to buy more of there products to prepare it for primer and they suggest you use their primer, all of which are expensive. Most of the other rust encapsulators can be used as a primer and painted right over.

The one major difference between the PPG and Rustoleum products and the products marketed to the old car hobby is the PPG and Rustoleum products are two part systems, the other are one part products. This I see as an advantage because as soon as you open the POR-15, and the other products, and the product comes in contact with oxygen it starts to harden. You can retard the hardening of the product by pushing plastic food wrap into the can to displace the oxygen, sealing the can and placing into a refrigerator but it will only slow the hardening, not stop it. Also, if you do put it into a refrigerator make sure there isn't any food in it because the fumes from the encapsulator will seep into the food, I know from experience. The two part epoxy system doesn't harden until the two parts are mixed together. Mix what you need.

The major benefit of the two part system is the cost. All of the two part systems I found are for the industrial market and come only in two gallon packages, on gallon paint, one gallon activator. The cost of the PPG and Rustoleum products is around $125 but you get two gallons, the cost for POR-15 and the others are around $40-45 a quart and around $150 for a gallon. Because the car products start to harden as soon as you open them I've bought it only by the quart so if I didn't use all of it I only lost a small quantity. I haven't bought the two part epoxy product yet but for my current project I am going to buy the two gallons for $125 and use it on my frame and underside of my car along with the inside floor boards, fender undersides and trunk. If I have any left over I'll seal it up and save it for another project or sell it to some one else doing a project at a cost cheaper than he'll pay for the other products.


I finally bought a two gallon kit of PPG Pittguard. I applied it three different ways to three scrap pieces of metal that were half sand blasted and half rust and on three spots on the rusted frame of my '37 Buick. On the rusty areas I only did a quick hit with a had held wire brush to get the loose rust off and then I wiped the areas off with lacquer thinner. The products out of the cans is very think. The paint is the consistency of honey or think latex paint, the catalyst has the consistency of peanut butter but when you mix them together the mixture starts to thin out a little.

First I used just the paint and catalyst, without any thinner. It took about 48 hours to dry but dried to a hard, semi gloss surface. PPG does have an accelerator but I didn't buy any. The surface turned hard enough that it takes quite a bit of effort to scrape off or scratch, not quite as hard as I remember the POR-15 product I used but it's very tough. POR-15 also dried a lot faster.

The second set of test pieces I mixed with the xylene, as per the PPG rep I talked to on the phone. The xylene can states it's a slow drying thinner for epoxy. It took a lot longer to dry, about 4-5 days, to achieve the same hardness as the straight mixture. It dried to a duller finish than the straight mixture. When it finally dried completely it was as hard as the first test pieces.

The third set of test pieces I mixed with lacquer thinner. The lacquer can states it's a fast drying thinner for epoxy. This mixture took about as long as the straight mixture and dried to the same hardness but duller finish.

One test I did not conduct is on clean new metal, I don't know if this product will have same problems bonding to new, non-blasted or rusted metal like POR-15 does. Unfortunately, I don't have much smooth metal on my Buick to work with with. The new metal I used in my trunk and on the floors I will dust with the blaster to get a texture.

I am not an chemist and don't have equipment to do a proper scientific procedure to test this product. I could have added too much thinner in the last two batches that could be the reason for the duller finish. Also, the can said pot life at 70 is 4 hours, I kept my shop down to around 65, a little cooler at night so that might have retarded the curing time.

I am happy with the results. This product, IMO, will stand up a lot better than regular store bought enamel or automotive paint and I think it's be just a durable a the encapsulators marketed to the auto hobbyists. It'll be a lot cheaper than products like POR-15 that cost $45 a quart, $150 a gallon. I paid $100 for two gallon kit, plus another $15-20 gallon for the thinners. I had to order this product from my local privately owned hardware store that sells PPG paint products. I'll have at least two gallons of product for 1/3 the cost. If I thin it some I'll get even more. I plan to use the straight mixture on most of my frame and parts of the body that won't be getting painted like the inside of the trunk, the top and bottom of the floor and the inside fender areas. I'll thin it a little to be able to have it flow easier into the hard to reach areas like the inside of the frame rails. I will blast everything before applying so it will have good clean surface to bond to. I am sure I won't be able to get to every spot inside the frame with the blaster so I am hoping the thinned product will find those places.


Last updated on April 22, 2010