There has been much concern over environmental cracking in pipe fittings used in gas and oil plants, leading manufacturers to develop new alloys that are resistant to galvanic and chemical corrosion. We at Chemipetro supply pipe flanges and other fittings in a range of alloys, including Super Duplex, to minimise the risk of cracking. Provided these pipe fittings are correctly installed, and the usual maintenance and checking procedures are in place, corrosion is not usually a problem.

However, corrosion can be a problem in older petrochemical plants, where outdated metals are married to new, noble alloys. Then, galvanic or bimetallic corrosion can occur, owing to the electro conductive nature of the process fluids. The increasing interest in marginal oil fields i.e. fields with uneconomical reserves has made the problem more acute.

Marginal fields are of little interest to major oil companies, but are attractive to entrepreneurs because of their low operating costs and overheads. These low costs are often down to the poor quality of the flanges used in the original plant design. In addition, the process fluids used in marginal fields are often highly corrosive. If these are tied in to older pipelines, with pipe fittings that were designed for more mildly corrosive processing fluids, corrosion can occur at the joints.

Seawater (or “sweet” brine) still poses a big threat to pipe flanges, and many studies have been conducted over the years on its corrosive effects. The effects of “sour” brine, i.e. seawater contaminated with acidic chemicals, are especially of concern.