Sour Service Tests
Corrosion and cracking in hydrogen sulphide-containing (sour) environments is one of our specialist areas of expertise. Failures in the USA and elsewhere in the 1950's resulted in NACE developing standards for materials for sour service, and standardised sulphide stress cracking test methods. These tests, and the more recently introduced guidelines for testing from the European Federation of Corrosion, are conducted in our well-equipped H₂S laboratory. Our staff are instrumental in developing these standards ensuring that the techniques in use of our laboratories are up to date and meet the latest requirements.

NACE TM0177 tests for sulphide stress cracking include Method 'A' smooth tensile tests. For these we employ Cortest proof rings and have capacity for more than 40 simultaneous tests.

Autoclaves are used to simulate the high pressure, high temperature conditions encountered downhole. We have a range of these pressure vessels with capacities in the range 0.25 to 40 litres. They are fabricated from Alloy C276 or Alloy 625, enabling us to conduct tests in very corrosive environments. These facilities permit tensile tests, bent beam tests, C-ring tests, slow strain rate tests and electrochemical tests at temperatures up to 650°C (625 only), 300°C (C276) and pressures up to 5000 psi in sour environments.

Formerly, slow strain rate testing was only covered by ISO 7539 and ASTM G129; these methods are for general use in any environment. NACE Test Method TM0198 for slow strain rate testing in sour conditions has recently been developed. The Corrosion division uses the slow strain rate technique with many clients.

NACE TM0284 tests for hydrogen-induced cracking of pipeline and, increasingly, pressure vessel steels are carried out on a regular basis.

Our staff here has a specialist knowledge of the sour service performance of many materials including carbon and low alloy steels, martensitic, superaustenitic and duplex stainless steels. We have published a number of papers on this subject, complimentary copies of which are available on request.