Inhibited pipe clamp prevents corrosion

Tom Shelley reports on a simple innovation that prevents pipe crevice corrosion on offshore installations Pipe clamps made from a polypropylene mix incorporating a corrosion inhibitor have been found to be successful in combating crevice corrosion offshore without having to resort to use of exotic and expensive grades of stainless steel. The material for the lamps has been developed by Stauff UK in conjunction with a US partner and overcomes oxygen differential cell corrosion in 316 stainless steel tubing in a marine environment, caused by the greater availability of oxygen outside the clamp than within it. Previous attempts to solve the problem have included: the use of protective wax containing vapour corrosion inhibitor, lead foil and use of 6 per cent molybdenum super austenitic stainless steel for all hydrocarbon duties. Stauff told us that during the early 1990s, effort was concentrated on developing a physical design that would exclude all moisture ingress between pipe and clamp. This failed to fully solve the problem as it was found to be impossible to prevent moisture gathering at the entry and exit points of the pipe within the clamp and this still allowed a degree of cell corrosion to develop. The new clamp with incorporated corrosion inhibitor, however, has been successfully tested in salt spray cabinet trials according to DIN 50021, ASTM B117 and additional sulphur dioxide tests. The new material has been designated PPAC and is to be marketed as the Stauff Anti Corrosion Clamp. It is a fraction of the cost of other solutions and is available in both standard single sizes and twin clamp series DIN 3015 Pt1 and 2 in metric and imperial sizes up to 25.4mm. Stauff UK