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Rust Never Sleeps
By Debbie Murphy/
Printable version
Degree of DifficultyModerate
Estimated Time240 minutes
240 minutes
Neutralizing Metal Corrosion -

It starts with a benign-looking bubble and grows, like the malignancy it is, into a metallic carnivore with the potential to consume a Hummer and then go looking for dessert. It's rust, the bane of anything metal and one of the greatest challenges for auto restorers.
Rust Never Sleeps
The Creep
No one is truly safe from rust. It first rears its bumpy head in regions with high rainfall and urban areas where salt is used on icy streets. But, even high humidity or beach communities in relatively arid Southern California feel the sting of rust.

To most vehicle owners, rust is annoying at best, and at worst it's a total automotive meltdown. For those hearty souls in the midst of restoring a classic that's suffering from long years of neglect, the bubble patch on the surface may be the symptom of terminal problems, like the proverbial tip of the boat-sinking iceberg.

No More Metal
The conventional approach to rust is to keep poking at it until you hit uncontaminated metal. In the most serious cases, that just doesn't happen. You scrape and sand and finally see the daylight through the metal. That's when it's time to turn to companies that specialize in providing replacement sheetmetal for body panels and floor pans. That's the extreme case, and we'll deal with installing panel replacements in a following article. For now, we're going to take a more optimistic approach: rust can be stopped, despite Neil Young's baleful song that "Rust Never Sleeps."

In any discussion of corrosion, it's important to understand exactly what it is, in scientific terms. The vehicle's steel is a combination of iron, metal impurities and negatively charged free electrons that are attracted to the iron atoms under normal conditions. All that changes when moisture is introduced—moisture in the form of actual water or simple humidity. Through electrolysis, the electrons abandon the iron and head straight for the metal impurities, forming rust.

Rust treatments, generally, start with elbow grease, removing the bubbles and pock marks with grinders, wire brushes, sandpaper or sand blasting, and taking the affected area down to bare metal. The more deep-seated the rust, the more aggressive the tools.

There are also rust paints available that seal or encapsulate the rust. These products are highly flammable and include toxic chemicals that require professional application. Acids can also dissolve rust, leaving a thin oxide coating on the surface. Like the paints, acid rust removal necessitates special breathing equipment. For high-end restorations, metal panels (or the whole car) can be submerged in a hot bath of caustic soda, stripping all the paint down to the metal. The panel is then treated in a tank of alkaline solution and the rust removed electrolytically.

Prior to these methods, the first "professional applicators" of the oldest method of rust treatment were probably blacksmiths. To protect their tools, the smithies would coat them with oil and heat them in their forges, not unlike the method of seasoning a cast-iron skillet. This process creates a hard coating, called magnetite, on the metal surface. This coating is chemically inert and will not react to oxygen or moisture. The path from the blacksmith shop to auto parts counter ran through the mining, construction and agricultural industries as scientists attempted to solve the problem of preserving metals exposed to the elements.

For modern automotive applications, rust converters come in the form of primers designed for use directly on the rusty surface, with no scraping, grinding, sanding or blasting. In fact, the product has to be applied to rust in order to work. The two components of converters are tannin and an organic polymer. Tannin, a water-soluble natural product derived from a variety of plants, reacts with iron oxide changing it to iron tannate, a stable blue/black corrosion product. The polymers provide the protective primer layer.
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