Drew Hevle is the Manager of Corrosion Control for Kinder Morgan, based in Houston, Texas. Mr. Hevle has a BS in Mechanical Engineering, is certified as an AMPP (formerly NACE International) Corrosion Specialist and Coating Inspector and has served as a NACE instructor and Chairman of the NACE Technical Coordination Committee (TCC), which oversaw all of NACE International’s technical activities. His hobbies are corrosion control and cathodic protection.
The global cost of corrosion is estimated to be $2.5 trillion, equivalent to 3.4 percent of the global Gross Domestic Product, according to the ‘International Measures of Prevention, Application, and Economics of Corrosion Technologies (IMPACT) Study’ developed by National Association of Corrosion Engineers (NACE) International in 2020. The study also estimates that between 15 and 35 percent of these costs could be saved by applying available corrosion control practices. Corrosion is a naturally occurring phenomenon commonly defined as the deterioration of a material, usually a metal, which results from a chemical or electrochemical reaction with its environment. A corrosion cell includes four components, an anode where oxidation and metal loss occur, a cathode where reduction and protective effects occur, an electrolyte (usually water), and a metallic path connecting the anode and cathode. Corrosion control practices mitigate corrosion by limiting or eliminating one or more of these components.
Corrosion Control Practices
Old school – if it moves, grease it. If it does not, paint it. New school – more sophisticated methods, including protective coatings, cathodic protection, environmental changes, material selection, electrical isolation, and design.
By applying corrosion control practices, manufacturers can reduce waste in manufacture, storage, and transportation. This will provide longer-lasting and more visually appealing products, increasing efficiency by reducing cost
The most common corrosion control practice is a protective coating. Types of coatings include barrier coatings that prevent contact with an electrolyte, inhibitive coatings that contain a chemical that prevent corrosion and sacrificial coatings like galvanizing that provide corrosion protection. Many coatings are a combination of these types, such as paint that contains zinc or aluminum. Old school grease is effective because it is hydrophobic, preventing water from contacting the metal.
Cathodic protection is similar to sacrificial coatings in using a more electrochemically active metal as an anode to corrode and protect the less active metal. Cathodic protection was first applied by Sir Humphry Davy, using iron anodes to protect the copper sheath of the hull of the ship HMS Samarang in 1824. A common example of cathodic protection in the household is the magnesium or aluminum anode in water heaters. Cathodic protection will prevent corrosion on a metal that is immersed in an electrolyte, so cathodic protection for things like an automobile is not effective (unless it happens to be submerged). Environmental changes include dehydration, for example, those “do not eat” packets that contain silica gel desiccant (please do not eat). Warehouse storage of high-value metal products such as aircraft and military equipment often uses dehydration to prevent corrosion. Other environmental changes include treating water in a fire sprinkler system to remove dissolved oxygen, making it less corrosive.
Material selection is used to prevent corrosion by selecting corrosion-resistant. Many household items are now made of plastic instead of metal, such as a leaf rake, not only because they are cheaper and lighter but also because they will have a longer life due to improved corrosion resistance. Gold is used in electronic wiring, either as plating or solid wiring, because its resistance to oxidation in some applications outweighs the much higher cost compared to copper. Chrome and silver plating, stainless steel, and the use of polymers in place of metals are all examples of using material selection to prevent corrosion.
Electrical isolation is used to eliminate the metallic path between dissimilar metals. A common example is a dielectric isolation union used to connect copper and cast-iron piping.
Proper design can eliminate corrosive conditions, like crevices, poor drainage, dissimilar metals, and others.
Automobile manufacturing is a good example of the evolution of corrosion control practices. In the 1970s, it was not uncommon to see significant corrosion on even latemodel cars, especially in cold-weather climates where road salts contributed to corrosion. By applying effective coatings, better material selection, including the use of polymers, and better design practices that eliminate crevices and provide drainage, cars today are much less susceptible to corrosion.
By applying corrosion control practices, manufacturers can reduce waste in manufacture, storage, and transportation and provide longer-lasting and more visually appealing products, increasing efficiency by reducing costs and the impact on the environment.
