دانلود کتاب Effect of NACE TM0284 test modifications on the HIC performance of Large-Diameter Pipes

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The test method described in NACE TM0284-2003 'Evaluation of Pipeline and Pressure Vessel Steels for Resistance to Hydrogen-Induced Cracking (HIC)' is intended to provide reproducible test environments capable of distinguishing the susceptibility of different steel samples to HIC in a relatively short time. Recently, several significant modifications have been made or proposed to the test procedure of this standard. Amongst others, these modifications affect the test solution chemistry, pH limitations and solution volume to specimen surface area ratio. Frequently, the acidified acetate buffer test solutions, as proposed in the EFC 16 recommendations and initially intended for use in sulfide stress cracking (SSC) tests, have been adopted for HIC testing. A frequent difficulty associated with the EFC 16 test solution A (pH 3.5) is the requirement of pH drift limitation within 0.1 pH units. The paper describes how to overcome the difficulty of frequent manual pH adjustment by automation of pH control and adjustment. Other HIC test modifications, e.g. with regard to changes in solution volume to specimen surface area ratios are also addressed. Based on the test results, the need for sophisticated modifications of the NACE TM0284 standard HIC test is discussed.