Re: Rust Prevention

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: : : I just bought a 1953 M-37. It is in OK shape body wise. : : There is areas of rust that need to be tended to. : : What is the best way to approach stopping it and preventing the continued : : spread of further rust. Especially on the underside of the bed and the fenderwells. : : Also, Is there a decent after market heater available that I can install? : : Gerry Zell : : PUCCINI@EROLS.COM : Hi, Gerry, : Rust is another of those entropy products. Eventually everything, including iron, likes to reach its most stable state. The idea in rust prevention is, of course, to prevent iron's self-destructive course by placing some effective road blocks in its path to oblivion. : There are several basic approaches one can take. Each has its pros and cons. Each will work better in some situations than others. This could get rather lengthy, but to avoid writing an entire text book, here are a few areas to explore: : Replacement of rusted areas with new metal. : Abrasive or chemical removal of rust. : Conversion of existing rust to a more stable oxidation state. : Sealing either bare or rusted surfaces against oxygen, water, and other solutions. : Use of either paintable or non-paintable sealers. : Applying a sacrifical anode coating (zinc cold galvanizing). : Hot-dip zinc galvanizing. : Electrogalvanizing (with optional chromate treatment). : Plating with a sacrificial anode coating (zinc electroplating). : Plating with a corrosion-resistant coating (nickel, chrome, etc.). : Chemical surface treatments (such as phosphating treatments). : Self-etching primers to improve adhesion of primer to bare metal (doesn't help much on rusted surfaces). : Primers with silica flakes that overlap to help reduce the porosity of the primer (such as Corroless). : Replacement of rust-prone parts with corrosion-resistant parts (such as stainless or special copper-nickel-iron brake lines). : Use of zinc bars as sacrificial anodes. : Use of electrical rust-prevention systems (quite interesting). : Many approaches use a combination of the above. Here are a few gotchas to keep in mind when trying to decide what method to use. : Zinc galvanizing (either cold or hot) is not a good base for painting. Paint doesn't stick too well to it, and the zinc layer is designed to slowly sacrifice itself to save the underlying iron molecules. : A galvanized surface can be made better able to accept paint with processes such as chromating. In general, galvanizing is good for areas such as door interiors, that won't be painted or seen. Also good between welded sheets. : Waxy, soft coatings are also good for interior areas. : Self-etching primers only have an advantage when used over bare metal. The etchant doesn't help when applying over rust or paint. : Always thoroughly clean and dry areas before coating. Some coatings have an affinity for water, which helps, but it still helps for the surface to be clean and dry. : Even if you have to leave some existing rust, make sure you always remove the loose rust before coating. : Don't depend on "miracle" rust treatments. There are some good products, but there is no perfect solution. : Avoid using rust conversion treatments that have an acrylic polymer additive. These are not good bases to paint over (in my opinion). If someone else has had good experiences with these, please come forth with the details. : Be careful when using acid treatments that not only remove rust, but also attack the virgin metal. : Alkalai treatments, such as caustic soda (sodium hydroxide/lye), can work pretty well if you can submerge the parts. These include hot baths and electrolysis methods. The latter is safer. : Some sandblasting treatments can work pretty well to remove rust. Aluminum oxide, silicon dioxide, garnet (cheaper), and zirconium seem to work well. Avoid silica sand. Glass beads will work, but they don't prepare the surface as well for painting. : A pneumatic (or electric) scaling tool is good for removing loose rust from thicker metal parts. Very noisy, but pretty slick for the looser deposits. : High-speed grinders with aluminum oxide sanding discs are OK for some things, but they tend to take good metal with them. : : One of the best ways of preventing rust is to wash the undercarriage after every dirty outing, or after driving on salted roads. Always wash out nooks and crannies where dirt can accumulate and remain wet for long periods of time. : Keep the vehicle covered with a breathable, but waterproof, tarp. Or keep it in a garage or under a carport. : Keep the battery compartment clean and dry. : Some good products? Well, there's a bunch of things that are good within certain limitations. Good old-fashioned Rustoleum rusty metal primer still does a pretty good job on existing rust. Corroless is supposed to be good (about $25.00/quart?). Two-part (catalyzed) primer sealers are VERY good for sealing surfaces. These are available in both self-etching and non-etching varieties, and often contain zinc phosphate, which actually contributes more because of its ability to soak up and hold the oils/resins/binders than because of its sacrificial anodic qualities. Urethane paints are known for sealing out nasty stuff, but have their drawbacks, too, such as expense and the difficulty of creating matte finishes. A good catalyzed acrylic enamel is usually the best bet for a top coat. Most MVs won't be using clearcoats. : Acid etch and phosphate treatments for bare metal can improve paint adhesion and can also provide a little temporary corrosion resistance while you're working on a bare metal part. These are simply wiped onto the bare metal, then rinsed. : Aluminum has a bunch of unique treatments as well, such as Alodining (not to be confused with anodizing), which chemically creates a corrosion-resistant surface layer on the metal itself. : Anyway, I'm sure I can think of more, but these should give you some terms to use in Internet searches or in formulating questions when you visit your autobody supply store. : Good luck, : Alan Bowes : (Salt Lake City, Utah)

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