Cars. As long as they make 'em from steel, we'll fight rust. In our desperation, we'll even gamble on exotic potions and remedies that promise to cover, neutralize, or eradicate the stuff. While our threatening arsenal of abrasives and chemicals vow to undo decades of decay, they may just reassign the damage to our own fragile innards. When elbows up in some caustic bath or hours into breathing pulverized silica, it's easy to wonder if there's a better way.
There is. For some time now, restorers who work with relatively delicate objects like clocks and antique tools have very effectively removed rust from intricate steel mechanisms and massive iron castings without damaging either the parts or themselves. Unlike caustic, acidic, or abrasive techniques, this process doesn't generate a toxic aftermath. Nor is it expensive. In fact, you could probably do it right now with the stuff in your garage.
The process is called electrolytic rust removal, and while it's been around for some time, it's probably one of the least-known methods. While it has its limitations, it's safe for both parts and the environment (see "Safety and Disposal" sidebar). It also has something else going for it that no other method can reliably duplicate: It can break the tenacious bonds that otherwise freeze rusty mechanisms and fasteners in their place. The newly converted often marvel at how easy parts disassemble after even a brief treatment. Curious? Read on.
How It WorksRust is the byproduct of an electrochemical reaction between positively and negatively charged electrodes in the presence of an electrolytic solution. In our case, the electrodes are the metal components of our cars. The electrolytic solution is nothing more than a fluid that facilitates an electrical flow. In this case, the electrolytic solution is the salt-laden water (melted snow and road salt) or mildly acidic solutions (carbon dioxide and water) in which our cars operate.
For rust to exist, two things need to happen: oxidation and reduction. When oxygen combines with iron, it takes electrons from the iron. When that happens, we say the iron oxidizes (gains a positive charge) and the oxygen reduces (gains a negative charge). Once that reduced oxygen encounters a lesser- or negatively charged part (through the electrolyte), it will surrender its spare electrons. When that happens, we say the oxygen is reducing the other metal.
Even though this reduction is unfamiliar, it's pretty cool and we can use it for our purposes. Here's how: If we reverse the polarity in that oxidation/reduction process, the same oxygen atoms that combined with our precious iron and robbed it of electrons will return that oxidized iron's missing electrons and break away from the iron. As outlandish as it sounds, it means the reduction process actually converts the oxidized material that clings to good steel back to a simple iron compound. While this converted metal skin won't replace lost metal and isn't as strong as the metal below it, it's stable and will take paint without rusting any further. After all, the unstable rust is gone. To pull this feat off, we just need to conjure up electrons. That's easy; we just have to intentionally oxidize a piece of scrap material.
True to our earlier claim, the process itself is very simple. Since electrolysis on this scale requires very little wattage or amperage, an ordinary six- or 12-volt car battery or battery charger does the trick (although the battery method requires an ammeter). Our electrolytic solution consists of nothing more than a basic mix of one to two tablespoons of sodium carbonate, otherwise known as washing soda, per gallon of plain ol' water. Any non-metallic container that holds both water and the part you'd like to scrub will do. The process requires scrap ferrous metal to act as an anode (positive charge); the part you'd like to clean becomes the cathode (negative charge).