Rust is the enemy of just about anything made of metal, and that includes your air compressor. Air-compressor tanks are especially prone to heavy rust and corrosion, especially if they're not taken care of properly. The following explains how rust develops in a typical air-compressor tank, as well as what can be done to stop rust in its tracks.
How Does Rust Form Inside Your Air-Compressor Tank?
The reason that air-compressor tanks are vulnerable to rusting out has a lot to do with moisture. There's plenty of it in the air you breathe, and some of it even gets into the compressor. Compressing the moisture-laden air beyond normal atmospheric pressure causes the moisture to condense from a vapor into a liquid.
This condensed moisture settles down at the bottom of the tank, while any water vapor left lingers within the tank until it cools down and eventually condenses. Of course, unprotected metal is especially vulnerable to rust and corrosion if it's exposed to heavy amounts of moisture.
How Can You Prevent Rust from Forming?
Draining the air-compressor tank on a regular basis is the most effective way of keeping rust and corrosion at bay. On most air-compressor tanks, this can be done simply by opening the drain valve located along the underside of the tank. It's usually a good idea to drain the tank of its moisture every time you use the air compressor.
After allowing all of the water to drain out of the tank, you'll want to keep the drain valve open for a couple of hours or until you need to use the air compressor again. Leaving the valve open gives the tank a chance to dry out completely, ensuring that there's no moisture left behind.
Should You Try to Fix the Rust Yourself?
If you find large amounts of rust particles or rust flakes in the moisture drained from your air tank, you might be tempted to take care of the problem before it gets worse. Some intrepid air-compressor owners may attempt to use phosphoric acid to eat away at the minor rust. Others may attempt to manually clean the tank using various methods. Needless to say, these measures often do more harm than good.
Any attempt to remove ongoing rust and corrosion from the interior of the air-compressor tank could actually weaken the tank structure. This makes the tank more likely to violently rupture in the event that recommended pressures are exceeded. In addition, any chemicals used to clean the tank interior (including phosphoric acid and other corrosion-fighting chemicals) could damage to the various seals and O-rings within the air compressor itself.
If you suspect that the air-compressor tank is rusting from the inside out, then it's usually best to replace the tank altogether.