Questions and answers in the adhesives, sealants and coatings industries.
Question: We have been using an anaerobic threadlocking adhesive for many years with no problems. Recently, we had a problem with one of our components rusting in use and began using stainless-steel fasteners and other components. Shortly afterward, we noticed the fasteners were not holding the required torque throughout our assembly process. Could the change in metal have affected the threadlocking adhesive? We have been very careful to assure all the components are clean, but the problem persists.
Answer: Anaerobic threadlocking adhesives generally cure by polymerizing in the absence of atmospheric oxygen, certainly an environment found between the threads of an assembled fastener. But the initiation of the reaction is also catalyzed by the presence of transition metal ions in a redox fashion. Transition metals with such activity include cobalt, copper and iron. Unfortunately, stainless steel contains a very high chromium component, which is not a transition metal, and experience has shown stainless steel to retard the cure of traditional anaerobic adhesives and sealants. Your threadlocker supplier should be able to provide you an alternative formulated adhesive or suggest a suitable primer that could be applied to the stainless surface prior to assembly.