There are a number of industries operating with various materials that can undoubtedly benefit from employing cathodic protection and remote corrosion monitoring. Aside from the traditional oil and gas pipeline market, where cathodic protection is vital, there are a number of applications within other, perhaps unexpected, sectors.
Here are four various applications.
Water storage tanks, typically made from a carbon-steel alloy, are common within many municipal water systems and generally come in two configurations: the ground storage tank and the elevated water tower. The effects or corrosion on the ground storage tanks can be detrimental, as it can cause premature failures and description in service during regular usage and during repairs. Traditionally, water tank designers will use protective coatings as their primary defense measure against corrosion, which is usually applied on the internal wetted surfaces of the tanks. These coating systems, however, are not a guarantee and will degrade over time.
There are two foundational types of cathodic protection systems: one is the galvanic system that relies on anodes made from metals that are more electronegative than steel. Thus, as cathodic protection applies to water tanks, zinc and magnesium are common anode materials used in water storage tanks. The second type of cathodic protection system is an impressed current system where longer-lasting anode materials can be used in conjunction with an external power supply, or rectifier, which converts AC power to DC current. For external water tank bottoms, this system is preferred as it typically boasts a longer design life than galvanic systems, and if properly maintained, doesn’t need to be replaced as often.
In addition to oil and gas pipelines, large diameter transmission mains that transport water and natural gas and biofuels over long distances, are also routinely protected by a combination of coatings and cathodic protection. As is the case for water tanks, an impressed current cathodic protection system (also known as an ICCP) or galvanic system can be used. Typically, an ICCP system is preferred for a pipeline that consists of a DC power source, an AC powered transformer rectifier, an anode, or an array of anodes buried in the ground. Sometimes, however, it makes better economical sense to use galvanic (sacrificial) anodes, especially in the case of pipelines with a smaller diameter and limited length.
Ships & Boats
The electromechanical corrosion of metal is perhaps one of the most detrimental processes that can affect a ship or boat in its lifetime. As cathodic protection systems are designed to alter a metal’s electromechanical characteristic via electrical current, this is often an effective measure to protect boats and ships from the damaging effects of corrosion. The metal components most at risk of corrosion include underwater fittings like propellers, shafts, struts, thru-hulls and steel and aluminum hulls. There are two types of corrosion that frequently affect boats and ships. The first is galvanic corrosion, which occurs when two or more metals with different galvanic voltages are electrically connected and wetted by water, and can occur in both freshwater or saltwater. The second is stray current corrosion, which occurs when underwater materials are energized by an electrical current that has strayed from an electrical conductor or device powered by a battery, generator or dock power, and is the result of an electrical fault.
Cathodic protection can successfully be applied to ships and boats, but it should be noted that too little protection inevitably results in corrosion, while too much protection can have equally detrimental consequences. A caustic attack to wood damage can occur from excessive cathodic protection, and is the result of a lack of control or an electrical fault. Similarly, a caustic attack to aluminum damage to an aluminum hull, stern drive or any other aluminum component can also be a result of too much cathodic protection.
Steel in Concrete
The usual suspects of salt, chloride and de-icing treatments are to blame for the corrosion of steel reinforced concrete for many years. Cathodic protection for steel reinforced concrete takes the form of an ICCP. While the metallized zinc cathodic protection systems operate in galvanic or sacrificial mode, metallised zinc cathodic protection systems can be, and are in many instances, operated in impressed current mode. An external power supply is often used and connected to the anode and the steel with the appropriate polarity voltage to deliver the required amount of electric current to the steel. In this case, the anode is usually placed near the surface of the concrete while the external power supply is installed nearby.
Undoubtedly, cathodic protection has proved useful across many industries and applications maintaining the structural integrity of the materials that make up vital commercial and private infrastructure. If you’re looking for more information about cathodic protection systems, or remote cathodic protection monitoring systems, check out Mobiltex for a wide array of solutions.