What is rust and why has it become important?

The oil and gas, as well as many other industrial sectors, are in a down turn – who knew?  We’ve been through cycles before, and there’s no telling when or how this one will end.  So what is an operator to do about equipment that is idled? This article discusses how to preserve equipment properly, especially during a downturn, and introduces one main form of corrosion that can be costly to operators if not prevented, rust.

According to NACE International, the cost of corrosion in the United States has been as high as “3.1% of the GDP”, but could also see reductions “between 15 and 35 percent” with better corrosion management strategies. Rather than walking away and doing nothing to idled equipment, there are very simple and inexpensive steps and best practices that can be taken to preserve equipment, either for easy start up or for resale value.

What all types of equipment need the right preservation methods and procedures? All lubricated equipment and parts, including but not limited to pumps, motors, gearboxes, engines, and other stationary equipment. 

There are two main types of corrosion: wet corrosion which includes uniform or general, galvanic, erosion, intergranular, and pitting (also known as dealloying, cracking, fatigue, crevice, and microbial), and dry corrosion which includes high temperature corrosion. What kind of corrosion are operators likely to see if their equipment isn’t shut down properly? Rust, a form of general corrosion, is a specific type of corrosion that occurs on iron and steel surfaces when both water and oxygen are present. Free water or very thin, almost invisible films of water, common in humid atmospheres, can promote rust. Since air, the normal source of oxygen, usually contains some moisture, and ordinary water contains dissolved air, the elements required for rusting are nearly always present.

Example of General Corrosion

Corrosion of some metals — copper and aluminum, for example — results in the formation of a tight oxide film that protects the surfaces from further corrosion. On iron or steel, however, rust is porous, allowing water and oxygen to reach the underlying surface and penetrate deeper into the metal. General corrosion or rust can be wiped away, but will leave pits. Bearings that have experienced this rust may operate, but will be noisy and therefore have shorter expected life.

If you are interested in learning more about building a robust rust prevention program, make sure to keep an eye out for our next article in the series, “How to build a rust prevention program.” To learn more about corrosion and other types of contamination, check out our Contamination Control Training.