Painting a Rusting Bobcat

I have just started to brush, scrape and grind off a lot of rust on the lower portion of my skidsteer. I am having a lot of difficulty getting all the rust off. Also most of it is pitted. What is the easiest way to get the rust off? I don't have a sandblaster, but have been using an angle grinder.
I have read to use POR 15 or similar products to 'lock in' the rust. Does this work? What can I do to smooth out the pitted areas? i was thinking some sort of bondo sanded down would at least make it look less pitted. What do you think?
I was planning on just buying several spray cans of primer and many spray cans of paint and seeing how it goes. Since the coverage of rust is about 40% I was thinking to just paint the whole thing. For the areas with no rust can I just hand sand, prime then paint it? I am not a painter and have no clue. this does not need to look showroom good, but need it to look better than it does today. I also want to do it the right way so rust does not come back in a year or two. This is a 2001 Bobcat 863, so it has some time on it!

Please give me some ideas. I got a few spray cans of primer and I will be headed to the BC dealer to get some white spray cans. Thanks for your help.

Mark

No experience with POR here. I'm assuming it's similar to the phosporic acid/naval jelly rust converters, with some protective coating. It will last as long as there is no oxygen getting through the the protective coating, then it will bubble up and flake, or worse yet, rust away under the coating.

I like to use zinc rich primer (or the spray can sold as Rustoliem "cold galvanizing compound"). It's not the same as galvanizing, but it gives you something to protect the metal when the paint gets scratched.

Either the POR or the zinc primer are compromise options. If you are willing to get all of the rust off, I think you can do better with better quality paints, but I don't know if they are available in cans, and I'm not the guy to ask about doing this RIGHT.

Are you using brushes and flap wheels on the grinder? If not, that might work much better than grinding wheels. If you have enough air compressor, a small sandblaster is pretty cheap. Especially if the pitting is bad enough that grinding isn't going to work.

I had my shop use POR over the arms of my Bobcat T200. My machine was a rental, and it spent a lot of its life doing concrete work. The arms were all beaten to heck, and the central section had cracked a dozen times and welded with varying degrees of skill. I had the shop take the arms off to rework and reweld the central section where the tilt cylinder attaches. I had wire brushed the arms fairly well, but there was still rust all over. The shop used the POR, and topcoated it with a few coats of Bobcat spray paint from a can. POR is amazing stuff. Once the can it opened, you'd better use it all. Unless you put plastic film under the lid, you will never be able to get it off. It's a one stage paint that does not require a catalyst. Moisture in the air gets it to kick off. Wear plastic gloves. If you get it on you, it's very difficult to get off. Once it cures, rust will no longer be a problem.

The finished surface is only as good as the preparation. You can spray POR, they say, but I don't know how you'd clean out the gun. A disposable roller works well. Boat bottoms are often "tipped," which is a process whereby paint is rolled on, and smoothed out with long strokes from a brush. The brush is not used to apply the paint, just tip the orange peel texture off of the rolled finish. With a little practice, this yields a very glossy finish. That might work with POR. I didn't need a beautiful finish, I was going for durability. POR is rock-solid.

The best way to treat your rust is going to be sandblasting. 2nd to that would be a coarse wire cup on on your angle grinder. Don't bother filling the pitting, you've already said it doesn't need a showroom finish and the bondo is a place for moisture to get trapped and cause future rusting. The POR is good stuff, follow the directions on the can. On a job this size, I wouldn't be touching spray cans, either use a spray unit with bulk cans or roll it on as has been suggested. With a fine knap roller the finish will be close to sprayed, good enough for an old machine.

All good responses. I will probably try the POR stuff and see how it goes. Once I put the POR on can that be sanded if needed? Also I heard that the POR dries black. If that is the case then with a couple coats of primer and a couple coats of paint do the trick? I don't want to see black under the paint, I want it to match as best as possible.
Where do you get replacement decals? If I paint the whole machine I will need to get some new ones. I have heard the bobcat dealer and possibly on ebay. Anyone get new decals and how much $$?

If I recall, POR dries a medium gray. I think it could be wet sanded. Water and moisture makes it harder. Top coating is not that hard. The shop doing my work is a mechanical shop, and they didn't have spray equipment, so I was limited to spray cans. My machine has been outdoors a full year, and what they did with the POR and spray cans still looks fine.

You can get decals from eBay. That's what I did. I can tell you that while the image looks similar to the original decal, it is not the same size. Before you sand or brush, take some pictures to make sure you know the proper location and measure the width of the image. You should be able to get something close. I don't think anyone looking at my machine would notice any difference, but I know the "cat" is a little smaller than the original.

MarkinMass:

I have used POR 15 on the underside of my pickup truck & car & on some equipment, & I am a big fan. I've found that the easiest & best place to buy it is directly off the por15.com website. Not only isn't the price anymore than at NAPA or others, but you can order everything that you need, & even get the POR 15 in different colors for multiple coats so as to visibly insure coverage.

My routine is to clean as must rust off as I can using whatever works (e.g., angle grinder with wire cup wheel or abrasive disc, wire brush, scraper, etc.), then use the Marine Clean product, then the Prep & Ready product as recommended. Apply 2 coats of POR 15 (different colors if possible) with a brush, then follow with as many coats of your finish paint as you need to cover.

It's a lot of dirty work, & by all means wear latex gloves or similar when using POR 15, because once it dries on your skin, you have to wear it off. Even acetone only touches it a little. When I was done under my truck, I looked like the Tar'Baby!!

Note that you have to cover the POR 15 with some finish paint if it is exposed to sunlight, because it is not UV resistant.

Good luck!