Materials Technical Group Meeting

Corrosion

13 October 2005
Chairman: Peter Boothby of Advantica

Corrosion is an issue that needs to be considered in all applications and there are a large number of ways of combating it. This meeting covered some of the problems and solutions in place in industry.

Following an introduction by the chairman, the presentations began with Mike Dale of MACAW discussing some common corrosion problems in ageing pipelines and plant. This acted as an excellent introduction to the day as he touched on subjects that later speakers took up in more detail. He outlined the main issues to consider when plant has seen arduous conditions; these include construction, mechanical damage, fatigue, corrosion and structural issues but crucially inspection was the key to detecting many of these problems.

Tim Illson of Advantica presented a corrosion control system that had been developed and put into place for the Atlantic Cromarty Development. This is a new subsea facility linking two wellheads in the North Sea in which glycol is added to the pipelines at the well heads in order to remove vapour phase moisture from the gas phase in stratified flow. Tim discussed the analysis involved in predicting the corrosion and other debris that might be seen in the 10-year life of the development.

Chris Fowler of Bodycote drew the morning to a close with an instructive talk covering the new standard for metallic materials in sour environments (ISO 15156/NACE MR0175). He explained how it differs from the standards it superseded (ISO 15156 and NACE MR0175) and how it is related to EFC16 and EFC17 which are still current. Maintenance and management details of the new standard were also discussed.

The complications of corrosion fatigue testing were outlined by Richard Pargeter of TWI. He explained that the variables of corrosion testing, stress corrosion testing and fatigue testing all of which are included in corrosion fatigue testing. This not only requires specialist equipment but also personnel who specialise in fatigue, corrosion and metallurgy.

The remainder of the day covered corrosion resistant alloys. Roger Francis of Weir Materials discussed some of the corrosion issues associated with superduplex stainless steel in oil and gas service. The main body of this talk covered two issues that are important today. Firstly external stress corrosion cracking from seawater dripping on hot process pipe and secondly hydrogen embrittlement of cathodically protected equipment.

The final presentation of the day was given by Chris Baxter of Outokumpu. He discussed the implications of post-fabrication cleaning of stainless steel. The very reasons for using stainless steel (corrosion properties, mechanical properties, cost and aesthetics) can be negated by inadequate cleaning. However, it is not always clearly identified whose responsibility cleaning is, or how and when it should be specified.

Lively discussion followed the final presentation, involving a number of the speakers and many of the thirty delegates.

Ruth Hammond