7/10/2023 0 Comments Nickel cobalt![]() The more hydrogen we have, the more likely we are to have hydrogen embrittlement,” says Rosas. “Hydrogen is everywhere: in the water, the environment, the air, and vapor phases. He notes the two elements form a stable, solid solution that can form a very hard, conductive coating that is able withstand temperatures up to 1,500 ☌, with properties that include abrasion resistance to guard against erosion, and kinetics that make it impervious to atomic hydrogen penetration and ingress that can cause steel to become brittle and crack. Nickel and cobalt are adjacent to each other in the periodic table of elements and are similar, highly noble metals-more noble than steel, says Rosas. Ni-Co alloy has been used in applications by both the military and NASA in environments where withstanding high temperatures and resisting corrosion are critical. 2 Additionally, the company notes that any plating process can produce hydrogen and in parts with hardness higher than 31 Rockwell C hardness (HRC), such as industrial fasteners, an uncontrolled plating process can lead to HE. According to Doxsteel, hydrogen is produced by sacrificial coatings as they oxidize, which can permeate the bolt and cause HE. Hydrogen can be produced by electroplating corrosion reactions such as rusting and the chemical reactions of cathodic protection (CP) systems and sacrificial coatings, which are metal coatings designed to corrode in place of the steel they coat. Garcia and Rosas explain that the presence of hydrogen is often a result of the unintentional introduction of hydrogen while forming and finishing the material (known as internal HE), but can also be linked to corrosion as well as corrosion-control processes (known as environmental HE). HE is caused by the ingress of hydrogen into metals such as steel and can seriously reduce a component’s ductility and load-bearing capacity, cause cracking, and lead to catastrophic brittle failures (e.g., a bolt becomes brittle and can break off) at stresses below the yield stress of susceptible materials. NACE International members Oscar Garcia and Omar Rosas, senior corrosion specialists with Doxsteel Fasteners (The Woodlands, Texas), note that SCC of connector bolts is caused by a combination of three factors: material susceptibility tensile stress and a corrosive environment, which can include the presence of hydrogen. The findings concluded that the connector bolt failures were primarily caused by hydrogen-induced SCC due to HE. The BSEE formed a Quality Control Failure Incident Team to investigate known failures and research possible causes. ![]() ![]() Leaks detected during an oil and gas drilling operation in the Gulf of Mexico pointed to failures from severe SCC fracture of bolts on the lower marine riser package. ![]() Electroplating fasteners with a Ni-Co alloy has been found to decrease hydrogen production on the coating’s surface and prevent hydrogen from penetrating the underlying metal bolt.Īccording to the Bureau of Safety and Environmental Enforcement (BSEE) (Washington, DC), many failures of bolts used to connect blowout preventers, risers, and other subsea equipment have been reported. Connector bolt failures due to stress corrosion cracking (SCC) caused by hydrogen embrittlement (HE) are a major problem for structures in many industries, including safety-critical equipment currently deployed in oil and gas operations. ![]()
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