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Understanding Cathodic Protection


Storage tanks are a ubiquitous feature of the fuel industry. Tanks are used to house a wide variety of substances, from gasoline, to natural gas, to heating oil. But many people fail to realize that such fuel sources often exert a highly corrosive effect. This can lead to the premature degradation of storage tanks, resulting in costly - and potentially dangerous - leaks and spills.

One of the most common ways to protect against tank corrosion involves the use of so-called cathodic protection. Unfortunately, many fuel tank owners fail to understand the nature of cathodic protection - often to their own detriment. If you would like to learn more about protecting your fuel tanks from corrosion, read on. This article will introduce you to the principles of cathodic protection.

Cathodic Protection

As noted above, cathodic protection functions to protect your tank from the corrosive effects of fuel. There are two main ways in which this goal can be accomplished. The first involves implementing a sacrificial anode cathodic protection system. This consists of a special anode composed of magnesium and/or zinc, which sits inside of the tank.

A sacrificial anode acts much the same way as the anode rod in a water heater. The corrosion-prone metals attract corrosion to the anode, thus sparing the walls of your tank. Over time, the anode will be gradually eaten away. Should it be consumed entirely, corrosion will once more start attacking the walls of your tank.

The second type cathodic protection goes by the name of impressed current. These systems also utilize sacrificial anodes. Unlike standard sacrificial anode systems, however, the anode in an impressed current system possesses an even greater ability to attract corrosion. This power comes from an electrical current passing through the anode. Impressed current systems also tend to boast longer life spans.

Cathodic Protection Testing

Both types of cathodic protection systems still possess only a finite ability to protect your tank. In other words, eventually the day will come when the system's protective abilities will be depleted.

At this stage, it is vital that you have a new anode installed as soon as possible. Otherwise, corrosion will begin exerting its detrimental effects on the vulnerable walls of your tank. To know the state of your cathodic protection system, you will need to have it inspected on a semi-regular basis. In Texas, the law requires that such inspections take place at least once every three years.

That said, most industry experts recommend that you have your fuel tanks inspected and tested on a more frequent basis, since this represents the only way to determine whether your cathodic protection system remains in good working order. Within a three year span, corrosion can easily cause serious problems.

Test Protocols

Most qualified contractors test cathodic protection systems through the use of a voltmeter and a reference cell. The voltmeter gives a reading of the voltage that exists between the reference cell and tank. A lower voltage means a greater degree of protection. If the voltage fails to fall below a certain threshold, the steel of your tank will be vulnerable to corrosion.

Certain circumstances may yield an unreliable test result. For instance, if the soil around the tank is frozen, the tank may seem to fail the test. In this case, the contractor will repeat the test as soon as the soil has thawed out. If the results remain unacceptable, the tank will need to be visually inspected and, if necessary, the cathodic protection system will need to be repaired.

Fuel Tank Experts

Ensuring the structural integrity of your system represents an essential facet of fuel tank ownership - and one that is required by law. For more information about having your fuel tanks' cathodic protection systems tested, feel free to contact the professionals at R & R Petro Services Inc.‚Äč