When it comes to the use of steel in the offshore oil drilling industry, there's no arguing with mother nature about it: corrosion is an unavoidable issue that must be dealt with on a regular basis.
According to Offshore Magazine, just under half of all new steel produced worldwide has been used to replace other corroded steel; specifically, 5.5 tons of steel degenerate every second around the world.
Today, at least two noted solutions have been employed at offshore oil rigs and other water-bound assets to help workers keep up with the pace of corrosion in the replacement of materials as they wear down with time.
Composite repair solutions with "sacrificial" layers
One tool known as a composite repair solution comes in the form of a corrosion-resistant epoxy-based coating or tape that is wrapped around piping to inhibit the rate at which their materials degrade. Due to the fact that managing the prevention of corrosion in materials is more time and cost-effective than simply replacing them altogether, engineers have embraced methods that use "sacrificial" layers to further slow down degradation rates.
Among other problems, sacrificial layers are a partial solution to what is known as corrosion under insulation, referred to in Offshore Magazine as "one of the most insidious problems for offshore assets" that is caused as a result of water trapped insulation surrounding steel. At the very worst, damage from CUI could lead to the shutdown of an entire facility or a surprise hydrocarbon release.
One type of composite repair solution is called Scar-Guard, which is delivered in rolls of laminate material that is wrapped around piping to shield pre-approved anti-corrosion coatings like liquid epoxies, tapes or shrink sleeves. While the material was first developed to "protect field joints and mainline coatings" from mechanical pressure and damage resulting from horizontal directional drilling, boring and microtunneling processes, according to Offshore.
A solution to galvanic corrosion resulting from graphite-based valves
More recently, a new valve technology has been developed in response to noted corrosion problems resulting from an electrochemical reaction known as galvanic corrosion, according to Oilfield Technology.
According to Oilfield, galvanic corrosion occurs when two conductive metals that have a large difference in oxidation potential are in close contact (such as welded or bolted together) and are "bridged by" an electrolyte, like ocean water. As a result, the least noble of the two conductive metals becomes more corroded, Oilfield explains.
While experts have recommended not to "mix metals" to reduce the rate of corrosion, most oil rigs are not designed to minimize the occurrence of such scenarios.
For example, one particular issue facing offshore oil rigs related to galvanic corrosion is the use of graphite, a non-metal which has coveted properties such as higher nobility and heat resistance than commonly used metals like steel and titanium. As the only non-metal capable of conducting electricity, the material is used for parts like gaskets, for example, because it is relatively easier to cut and fit, according to Oilfield.
Still, graphite's use with other metals has resulted in an expedited corrosion process compared to the use of the same metals.
Graphite has been used to replace asbestos-based materials, according to Oilfield, and its impact on the rate of galvanic corrosion when coupled with metals has been studied in-depth since the 1990s, when the Navy Surface Warfare Center specifically tested graphite epoxy composites.