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Dozerboss
05-26-2004 22:54:55
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Re: Re: Por 15 rust paint in reply to Dave42H, 05-26-2004 18:42:56
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Well I'm not a pro painter, but will share what i have learned. I have had no problem topcoating the Por 15 except where it is too thickly applied and "bubbles" (small pore like craters). I am using epoxy primer straight over the Por 15, then acrylic urethane as the finish coat. The Por 15 shine will quickly fade if you leave it exposed to the sun. I have painted over fresh (shiny) and faded Por 15 black with no lifting problems. I expect my material thickness is too much in some places as well, due to having used a foam brush in hard to reach areas such as the bottom of the track frame. But since we're talking dozers, it's impossible to keep paint around the undercarriage and anywhere it will throw dirt around. So my goal is to use the toughest materials so it will last as long as possible. What I expect is the dirt will wear the finish coats away first and the Por 15 will last longer and prevent some areas from going all the way to bare metal. If you do get Por 15 on too thick, it will leave those air bubbles that will not accept top coat - you will see the black in the bubbled areas if you top coat it like that. If you want to try to fix that, then sand that part or nib file or run razor it back down. The good news is it still protects the metal underneath. I have not seen any rust bleed on the bubbled areas of my undercarriage, I have a few areas like that where the the rollers and rock guards will bolt up. When they are bolted up, you're going to tear some paint anyway. This is what happened when I put the sprocket back on, the top coat tore but the Por 15 stayed! My preference was to unbolt everything use por 15 and touch up the inevitable paint tears rather than paint already assembled and leave the rust in there. This is the process I am using - Rust remover on the bare metal for 30 to 60 minutes. Currently using Oxy-solv which leaves a zinc phosphate coating for paint adhesion, you take it off with wax and grease remover. I will be trying another brand when I run out of it. They have a liquid and a gel, the gel dries too quick and gets too thick leaving a heavy residue, so I don't like it as I have had to wire brush and do some parts over with the liquid type. Next 2 coats of Por 15. So far I have let it dry completely then applied the epoxy and finished with the urethane over the epoxy within 30 minutes. I am going to try epoxy over tacky Por 15 as suggested by another user. Hopefully to improve adhesion between epoxy and Por 15. I painted some rims using the let it dry method. When tires were put on, the machine scraped through the urethane to the epoxy in some places, and in others through both epoxy and urethane, but nowhere did it go through the Por 15. I have not spent the extra money for the Por 15 special tie coat primer, I suspect it is no different than any other brand of sealer, but that is my opinion. I would rather spend my $ on epoxy and not have that extra thickness of the sealer in the paint film. With it's hardener, I think epoxy is aggresive enough to stick onto Por 15 without sealer. Another factor is the dozer has a lot of cast steel and pits anyway, so sanding primer or Por 15 is hit or miss. When I get to the top, I will wet sand the old finish on the smooth surfaces like the hood and use Por 15 only where the rust can't be removed, let it dry and scuff sand it before priming and finish coating. You have to be practical with a working machine like a dozer. I'm going to do the best prep I can on it knowing there are areas that are impossible to sand and hopefully will end up with the longest lasting paint job you can expect on a machine like this. I think the Por 15 is a much better alternative than just painting over rusted areas like a dealer would do to resell a machine. What we need is a product like Por 15 that you can apply to spot rust on parts that still have good top coats and will adhere to the existing paint too. Por 15 is not recommended for that, Extend is supposed to work for that, but I have never seen it do it, plus it's a latex and won't work with automotive type paints. I don't use it anymore, maybe it will work fine on old metal yard furniture and brush on paints like rustolem that the ladies like. (Rustolem was great back when they used lead in it, but in my opinion it has no place on anything except wood) One exception is their tractor line, i have used it on a sprayer bracket where i didn't want to go to the trouble of buying and mixing more expensive material for a small part. For a single component paint it has held up good on a shed kept sprayer, but i wouldn't paint a whole machine with it. I am using PPG's Omni brand for the primer and top coats and their cleaner degreaser. I am satisfied with the gloss of the urethane using a 1.3 hvlp gun. I started with a 1.4 as they recommend, but the result was a duller finish. I choose urethane because it is tough, and keeps its gloss even in constant sun exposure. All the fuel trucks in my area are repainted with it because it holds up when fuel spills on it. It's hot where I am, so that is a factor too in getting a good wet coat with good gloss. Let me know what your results are, I am working piecemeal so if somebody out there has some suggestions I'd like to hear them. The Eastwood company has a product like Por 15, but I think it too is for bare metal and wouldn't help with spot rust. The tire machine I referenced really says alot for how well Por 15 sticks to bare metal treated with zinc phosphate. I'm satisfied the money I spent on Por 15 was worth it. I'm just not convinced you need their entire product line to be successful, so I'm using up what I have on hand, like the oxy-solv, instead of scraping it to buy their version of the same thing. I sucessfully thinned the Por 15 with thinner from a similar product (they say only use their thinner) called Miracle Paint and sprayed it on my rock guards. Again just using what I had on hand instead of wasteing it. The next time I spray it, I will need more thinner and will use their brand. I have no idea what size tip as I used a hvlp touch up gun, and in order to make it work, I had to remove the air cap occasionally and pour lacquer thinner through it to prevent clogging. The finished texture was excellent, I thinned it 20% and I will be using that technique when I get around to the other side of the dozer instead of a careful foam brush technic as was used on side 1. The foam brush leaves a good texture too. You can't see any brush marks in the top coat, looks like an auto quality job, but it is labor intensive to do it that way as the foam loses it's stiffness quickly and you have to change brushes a lot-wastes paint and $ on brushes. Another tip is to buy a plastic top for your quart can with built in pourer and screw on top. If you have Lowe's where you are, you can get one there. Then you can pour out what you need, wipe the pourer with thinner, and put the top back on with cling wrap under the top. At first I followed their directions and dipped it out with a coffee scoop, this wastes a lot of it. Like they say on the can, don't let it get in the grooves and put the top back on. You won't be able to get it off. One of the cans I ordered came with the top stuck on like that and they replaced it. I also heard you can spray it with a undercoating gun. I would think that would leave too thick a coat. Anyone with Por 15 experience - please post!
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