Inliners International Forums General Discussion Body & Paint Aluminum oxide blasting & rust-through questions

I have a question concerning how to handle some rust through areas on my ’39 Chevy. I know that the best approach is to cut out and weld-in new, but this will not be a show car and I am trying to prevent having to outsource any welding.

I will have this fender (as well as the entire car) aluminum oxide blasted. After the blasting, can I fill the area with good quality body filler (assuming all rust has been removed) or should I treat the area with POR-15 coating and then use the body filler? Does anyone have any opinions on the POR-15 products (metal prep, coatings, primers, and body fillers)? Also, does anyone have any opinions on aluminum oxide blasting in general?

Your help would be greatly appreciated.

When media blasting a car, try to ask for Walnut shell blasting. If the rust is really intense, I would hand sand that area. Aluminum Oxide, if applied heavy to remove bad rust, might warp your sheet metal.

I've used POR 15 and it is fantastic for covering and eliminating future rust. Make sure you use their primer. It would be hard to paint over their paint. Also, POR 15 is like Powdercoating an item. It's nearly impossible to get off even when sand blasting! It's not impossible, but difficult. It's a great product. I did all of my suspension and chassis with it. It still looks like new after 5 years!

RapRap
1940 ChoppedChevyCoupe

As you state, removing the rust, and then cutting out the weakened areas and welding in new is the RIGHT way to do it. If you can't afford to hire it done, then try looking into buying a MIG welder and learning to do it yourself. A decent 110V MIG can be had for under $500 with tank, just make sure you have a 20 amp circuit to plug it into. 15 amps will not work. How much bodywork can you hire done for $500? almost none...

I have never used the aluminum oxide, just silica sand. Make sure you use a respirator whenever you do blasting. No matter what you use for blasting media, its only going to get into the pits that are larger than the media. So the smaller the grit, the cleaner you will get it. Using a chemical remover like Oxi-Solve is another way to do it, but is slower than blasting. I usually blast to get most of it off, then soak in Oxi...
Be sure to keep moving and don't use too much pressure, or you can warp larger panels like trunk lids, quarter panels, etc... been there, done that...

Whether you decide to use something like POR-15 or not, it is best to clean up the metal as best as you can first. I have used it alot without problems, but you should always top coat it. Bodyfiller does NOT stick to it, and it doesn't like to be sanded, so I always spray on a coat of primer just as the POR becomes touchable, usually 1-4 hours after appllication, depending on the weather conditions and temperature.
Make sure you wear a respirator and cover yourself up when using this stuff, as it contains some pretty nasty chemicals. If you get any on your skin, you will be wearing it for a week. I have not found it to be as physically durable as RapRap suggests (like powdercoat), it comes off easily with paint stripper, and if the surface prep is not done right, it can be pealed off in sheets. Its better to brush it on than to spray it. I have never used anything from POR-15 other than the black or clear rust covering paint, and the Pelucid clear coat. I have some of there High-temp stainless paint, and there Glisten (sp?) 2 part clear coat, but haven't used them yet.

If you try the old screen and bondo trick to fix the holes, you will find that the filler will likely get hairline cracks wherever there is a metal edge under it. That is why you never use it to fill holes or seams. You always WELD them shut, and use filler to smooth and shape.

Most "internet experts" will tell you to clean the metal, weld in new patches, use EPOXY primer (like DP90) and then a sandable primer like K36, and don't waste you money on things like POR-15. Some will say when using body filler, to apply it directly onto the metal, others will say only over primer, and I say that I've done it both ways without any problems, and I will continue to use the POR-15 until I prove to myself that it isn't useful.

When I first used POR 15 they had only a few products. They now have a catalog full. Check it out at www.por15.com and order a catalog. They have their own primer and body filler, ect. I have used their products with great success and have an order in now for products I have not tried, but considering their track record so far I am not at all worried. They have a primer that allows you to paint right over cured POR 15. It is worth investigating. You can buy small amounts of their products and that makes for a less expensive "try it out". I am not a body man, just a shade tree sort who finds out about things by "fooling around". I tried spray and brush and brush is best in my limited experience. They give complete instructions and have on line help. Ignore their instructions at your peril. (personal experience!) Ray

Another twist,

I recently had my truck cab cleaned to remove the old pain using baking soda. It environmentally friendly and won't warp sheetmetal. It dosen't attack rust though, so we followed it up using a 50 grit sanding disk to get the rust off. Once cleaned we coated the entire cab with a 2 part epoxy primer - 2 coats.