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Sunday, 09 January 2011 14:52

Car Painting Tips

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One of the most time-consuming and expensive projects you'll ever perform on your Mopar is to either paint it yourself or have it painted. Paint and bodywork have long been considered an art more than a mechanical procedure. a good paint job is certainly the result of many hours spent welding, sanding, and preparing the body for paint. In fact, rather than the common misconception that a "paint job" is a single step process, painting a car is really a multi-step process that leads up to the actual painting of the car. Being a good painter requires a lot of patience and a certain amount of perfectionism because that new, glossy paint job will reveal the slightest blemish underneath, but what's necessary to perform proper bodywork? We visited J.D.'s Paint and Body in Mulberry, Florida, to find out exactly what it takes to produce show-quality paint jobs, and to get hints about what you can do yourself to help the process.



The first step to a great looking paint job that will last is having a solid, rust-free foundation to work from. Rust is a common term for the process of steel oxidizing and is normally caused by unprotected metal being exposed to water or water vapor. Adding salt to the process, as in salty roads in the winter or beach driving in the summer, only expedites the process and can quickly turn sheetmetal into an ugly, flaking, rusty mess. The worst issue of rust is that once the oxidation process has started it's very hard to stop. Even taking away the source of the moisture won't stop the metal from rusting in a self-destructive manner, so the only choices are to remove the rust completely or to stop the process of oxidation chemically. Either way, the rust must be completely removed or treated or it will return under the paint, causing unsightly bubbling.

The best way to ensure that rust won't return is to completely remove it from the car. This can be accomplished by removing the metal just in the rusty area and welding in patches, but extreme cases may require replacing the entire panel. While doors and fenders are easily replaced by bolting on the new parts, quarter panels, door skins, and floorpans are more difficult and require specialty tools such as a welder, clamps, spot weld cutter, grinder, and cut-off wheels.
Painting Your Car Rust Removal
Before even considering colors...

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Painting Your Car Rust Removal
Before even considering colors or a paint booth, all the rust must be found and either removed or chemically neutralized.

Whether removing the metal due to a collision or due to rust, the methods are the same. Cut out the affected area, fabricate or purchase a patch panel, fit the panel, and weld it in place. The welding process can be a trick in itself as the heat created in thin, sheetmetal panels can cause distortion, leading to additional time spent straightening the welded-in panels. Coating the panel with a heat-absorbing compound and stitch welding (welding short segments slowly) the panel are two ways to keep the panel from warping while being welded in place. An additional concern of welding is that moisture can be trapped inside any areas of porosity, leading to future rust problems. Priming the metal in a weld-through primer and sandblasting the area after being welded are two ways to ensure the area won't rust in the future.

Most areas of light surface rust don't require metal replacement and can be chemically treated with a liquid rust inhibitor. OSPHO is a common brand, but other manufacturers, such as POR-15, make liquid rust inhibitors as well. Rust inhibitors are also found in gel form, such as naval jelly. No matter the brand, all rust inhibitors work basically the same way. Their main ingredient is phosphoric acid, which converts iron oxide (active rust) into iron phosphate, chemically stopping the oxidation process. Parts can be dipped in rust inhibitor, but the more common method is to spray liquid inhibitor on the area from a spray bottle. Depending on the severity of the rust, it can take from 2 to 12 hours for the phosphoric acid to completely convert the rust to iron phosphate, which is black in color. Remember this process is only effective on areas of surface rust that are not flaking or rusted through. Those areas should be cut out and replaced.

It's not until all the car's rust has either been removed and replaced with new metal or treated with rust inhibitor, that we can call the first step in our painting process complete. Now we have a solid foundation to build on, we can begin straightening and filling warped panels and correcting other imperfections.

Painting Your Car Paint Bubbles
The most common cause of paint...

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Painting Your Car Paint Bubbles
The most common cause of paint bubbles, like the ones shown on this Demon, is not removing or properly chemically treating the rust underneath before paint is applied.

We've all heard someone at a car show or cruise say that their car has all new metal with no filler, that's why it's so straight. Well, we have news for you, nearly every body panel we've seen-new, N.O.S., or used-requires some filler to be made straight. Straightening the panels is likely the most time-consuming part of performing automotive bodywork. While some panels may be straightened with a hammer and dolly, most require filler to be perfect. It takes many hours of spreading body filler, sanding, and repeating the process to ensure a panel's straightness, and, again, some specialty products and tools are required. First, it is important to use quality body filler. Cheap body filler may fill the voids and imperfections of car's panels, but it won't last nearly as long as quality filler. Another benefit of quality filler is it's usually easier to sand than its cheaper counterpart, requiring less time to perform the job.

After the filler is applied to the panels, the key is to sand, sand, and sand. Most of the sanding can be accomplished by using power sanders, random orbital units, and air files, but the final steps are always performed by block-sanding the vehicle by hand



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