In addition to ensuring that water is never allowed to enter or form inside your tank, you should take the following precautions in handling and maintaining your scuba tank.
- Do not store tanks that are full of air for prolonged periods of time (no more than 3 months. A tank should be stored with just enough pressure (200 psi) to keep moisture out. Remember the higher the tank pressure, the greater the corrosion that may form inside.
- Your tank should receive a visual inspection at least once a year. If the tank is in constant use or in constantly filled around salt air, then it should be visually inspected every three to six months.
- You must have the tank hydrostatically tested at least once every five years. This should only be performed by a reputable hydro testing facility that is able to totally service your tank, include testing, cleaning, drying, zinc coating, and painting.
- Always give your tank a fresh water rinse before putting it away. Be sure the tank valve is closed when running water over it.
- Do not overfill your tank past stamped ratings. This place too much stress on the metal, causing the tank to weaken over a period of time. Overfilling a tank time after time is hazardous and can weaken the metal.
- Avoid rough handling that will cause dents, gouges or nicks in the tank. This can invite corrosion of the metal and can also weaken the cylinder.
- Always store tanks in a vertical position unless otherwise recommended by a visual inspector. If there is any moisture in the tank, corrosion may form at the bottom of the tank, which is the thickest part of the tank wall.
- If you see or smell anything coming out of the tank valve, corrosion or contamination may be suspected. If you rap on the side of the tank and hear anything rattling around inside, the tank must be opened for a visual inspection.
- If water is found inside the tank, but corrosion has not yet become pronounced, the tank can be rinsed in fresh water or steam cleaned, then dried thoroughly with warm air. It is always best to let a qualified inspector determine the extent of the corrosion.
- If you suspect anything wrong with your scuba cylinder, always have it visually inspected by a professional dive shop or a reputable repair facility.
Keeping Moisture Out of Your Tank
The obvious way to prevent corrosion in both aluminum and steel tanks is to prevent water from coming in contact with the tank metal for any length of time. The following recommendations will insure that water will not have a chance to damage your tank.
- Never drain the air completely out of a scuba cylinder, and never leave the valve open if you do. If you do drain a tank completely dry during a dive, close the tank valve immediately. Then, at the earliest opportunity, the valve should be removed to check for water in the interior of the tank.
- Never let the air escape from the tank rapidly. if you must let the air out of your tank, do it slowly. the best method is to immerse the tank in shallow water with the valve above water, and slowly let the air escape. Emptying the tank in a hurry will cause condensation of moisture to form on the interior of the tank. As the air inside expands rapidly, it will also cool very rapidly, giving up some of it’s vapors in the process.
- Make sure all fittings are dry when attaching a regulator or a filler nozzle from a compressor to the tank valve. One way to insure this is to momentarily open the tank valve and purge it before filling the tank or attaching the regulator. This will blow away any drops of moisture that may have accumulated near the opening. If even a few drops of water enter the tank, they can cause corrosion inside the tank over a period of a few short months.
- When washing your tank, pay attention to the tank boot and the backpack attachments. Water trapped in tightly fitted areas may enter small nicks and scratches and begin corrosion on the exterior of the tank.