For decades, the leading coating system in refineries and power generation facilities has been Polytetrafluoroethylene (PTFE). PTFE gained prominence in the early 20th century under the name Teflon where it was used to coat everything from non-stick cooking pans to valves and pipe seals at the Manhattan Project’s uranium enrichment plant. PTFE-coated “blue bolts” have been a popular bolting choice for many oil & gas facilities in upstream, midstream, and downstream operations since the discovery of PTFE, which has led to years of improved industry bolting practices and increased operational safety.
However, despite decades of admirable service, PTFE is having difficulty standing up to some of today’s more difficult bolting challenges. PTFE easily chips during bolt installation, compromising its protective properties right from the start. Sometimes the outside of the PTFE coating will appear undisturbed, but the steel it’s supposed to protect is corroding underneath and the threads will seize. The -50°F – 350°F operational temperature range of PTFE excludes it from service in high temperature applications such as heat exchangers, and PTFE in sour water environments can do very little to protect from corrosion.
How the Industry Has Responded
In recent years, the industry has called for higher standards in bolting operations. Facilities want carbon steel bolting that can operate in high temperature environments so they can avoid using expensive exotic metals. The industry needs a viable carbon steel option to pick up the slack when PTFE cannot be used in petrochemical and power generation applications that will keep bolting costs controlled while improving worker safety.
A novel coating system gaining traction for refinery and power generation uses is ASTM B994 SC18 Class 1 Nickel-Cobalt alloy. Like PTFE, Nickel-Cobalt has a long history in other industries, starting with its use on the Saturn V rocket. In recent years, companies have applied the alloy to carbon steel bolting. The hardness and adhesion properties of Nickel-Cobalt far outclass PTFE and the electroplating and testing processes described in ASTM B994 Class 1 specifications make sure the plating is not susceptible to mechanical damage. If the coating is damaged by other means, the damage does not grow or extend, even after exposure to corrosive environments.
Since ASTM B994 SC18 Class 1 coating adheres to the bolt, and Nickel-Cobalt alloy has very low hydrogen permeation, it acts as a barrier to environmental sources of hydrogen to greatly reduce the risk of hydrogen embrittlement. Its -328°F to 1300°F operational temperature range makes ASTM B994 ideal for use in heat exchangers and other high temp applications such as ASTM A193 grade B16 studs. ASTM B994 Class 1 testing can reliably predict the life cycle of each production batch. When faced with environments that challenge PTFE coatings, ASTM B994 SC18 Class 1 Nickel-Cobalt is in a class all its own.
To see a real world comparison of ASTM B994 bolting to PTFE blue bolts, read our recent case study. To learn more about how ASTM B994 SC18 Class 1 bolting can protect your refinery operations, contact Doxsteel Fasteners today.