Cathodic delamination at the polymer-to-metal interface of sea cable connector assemblies

摘要

Electrical and fibre optic cable connector assemblies are often required to operate under the very harsh environmental conditions experienced in the offshore oil and gas industry and on ships, autonomous underwater vehicles and remotely operated systems. These assemblies are frequently the source of failure and so must be sealed, mostly at the metal connector-to-cable interface. This is normally achieved using a polyurethane (PU) encapsulant system that bonds at the interface between the metal connector back-shell and the cable. In environments where sacrificial anodes are used, however, cable connector assemblies are prone to cathodic delamination (CD, oxygen reduction increasing OHconcentration at the PU/metal interface), which can compromise PU-to-metal bonds causing failure. Materials that are resistant to CD failure are therefore highly desirable. New EC REACH legislation has further regulated the use of hazardous chemicals in the production and use of polymers. New, compliant materials have emerged, although lack well-established performance testing. Hence, in this work, stainless steel 316L, bronze CW451K, titanium Ti6Al4V, PU and commercially available primers (PR24 and PR91) were used to investigate CD failures in cable connector assemblies and galvanic coupling effects. Data obtained from long-term sea raft exposure trials and flowing natural seawater tank tests were used, for the first time, to validate short-term accelerated laboratory salt-spray testing of these materials. The failure rate due to CD was observed to decrease in the order: electrochemical potential polymeric system metal substrate, strongly suggesting that electrochemical potential has the most dominant effect on CD failure rates.