RIASSUNTO
Many outboard cable connectors fail because of a process called “cathodic delamination” (henceforth: “CD”). The driving force for CD is the cathodic protection system used to prevent susceptible metals comprising ship and submarine hulls from corroding in the marine environment. Outboard cables are often grounded or attached to the hull of their parent vessel, from which they unintentionally pick up the protective cathodic current. The voltage used in these protective systems causes dissolved oxygen present in seawater to be reduced on exposed metal surfaces, leading to the production of hydroxyl anions. These anions create a very high pH microenvironment immediately above the cathodically polarized metal surface. The pH at the metal surface is sufficiently high to cause most polymers, paints and primers to debond rapidly from said surface. This enables seawater to debond polymer encapsulants from metal connector backshells, thereby allowing the seawater access to the interior of the connector, where it can short out, corrode, or otherwise damage, wire connections therein. Many marine hardware designers have tried to slow or prevent CD on connector backshells by applying coatings “resistant” to the high pH generated by the CD process. These efforts have met with limited success. Because the CD process requires positively charged cations to move to the zone of active debonding to charge-balance the negative hydroxyl anions being generated there, constrictive bands both above and beneath the surface of the encapsulant have been suggested as possible means for stopping the progress of CD down the length of a connector backshell. The results obtained from the application of exterior titanium bands and interior PEEK bands to connector backshells on the effects of CD will be discussed. In addition, changes to the design of connectors protected from CD by non-conductive ceramic (NCC) coatings that provide longer-lasting CD protection even in the harshest CD-promoting environments will also be presented. None of these techniques require changes to the coatings or encapsulant materials already in use on outboard cable connectors, and one of the methods (external bands) can even be applied to a connector after it is manufactured and installed. The results to be discussed suggest that the best, longest-lasting protection from CD will be obtained from both the use of CD resistant coatings and various mechanical enhancements designed to protect the vulnerable metal-polymer bonded interface.