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The coatings industry has made widespread use of a variety of accelerated test methods to quickly and effectively evaluate coating performance. Such accelerated methods are advantageous for predicting coating system performance where real-time testing is impractical. For example, it is not practical to evaluate coatings in harsh environments where coatings are expected to last for decades when the pace of innovation and new coating development is faster than the test time would need to be. Therefore a variety of test methods exist to evaluate coatings on metal substrates, such as steel or aluminum. Coatings that will be subjected to corrosive environments require testing in environments to simulate the effects of corrosion, typically involving exposure to moderate salt concentration and elevated temperatures for a specified amount of time. Such tests, testing environments, and evaluation methods include ASTM B117,ISO 9227, and ISO 12944, to name a few.
Accelerated corrosion tests are commonly used across the coatings industry to predict performance of coating systems and aid development of new coating systems for a variety of exposure environments. Variability in the results exist in almost all accelerated testing. To improve efficiency in coatings development and to gain better confidence in test results, it is important to understand the root cause of variability. This work investigates the effect that different scribe requirements (such as dimension or orientation) have on the outcome and comparability of accelerated corrosion test results. Discussion will focus on coating application and sample preparation prior to accelerated corrosion test exposure, as well as evaluation of scribe corrosion after various preparation protocols.
Aircraft representative galvanic test articles and witness coupons were placed out for atmospheric exposure testing at the U.S. Naval Research Lab (NRL) site in Key West, Florida. One set of test specimens was exposed to only ambient environment for a 62 day period; a second set of test specimens was exposed to both ambient environment (initial 62 days), and a short duration, twice daily, seawater spray protocol over a further 55 day period. Environmental loading was monitored using sensors that measured temperature, relative humidity, rainfall, and time of wetness (TOW), at 30 minute intervals. Following retrieval, the test articles were inspected in the laboratory using laser profilometry to characterize the spatial distribution and depth of corrosion damage. Mass loss measurement using the witness coupons was used to estimate relative corrosion rates for the two periods.
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More and more High Pressure High Temperature (HPHT) sour wells are operated worldwide. Challenging material selection is required for such severe operating conditions.1,2 Very high strength materials, presenting yield strength above 896 MPa (130 ksi), are required for sustaining the pressure. Consequently, even a low amount of H2S in the gas phase may lead to a H2S partial pressure beyond the limit of 3.5 mbar (0.05 psi) established in NACE MR0175 / ISO 15156 standard.3 Indeed, both high yield strengths and partial pressures of H2S contribute to a situation where the risk of Sulfide Stress Cracking (SSC) is high. The present paper is focusing on the SSC resistance of 130 ksi minimum yield strength material developed for covering such HPHT applications.
EWPD of Saudi Aramco is the custodian of five large volume crude oil storage tanks with diameter of 106 m (348’) and 110 m (360’), where the crude oil is stored and transported from eastern region to western region. The tank which is being addressed in this paper is an API1 650 with floating roof. Its capacity is 1,013,000 barrels and its diameter is 110 m. This tank was built in 1978 on an oily sand pad and reinforced concrete ring wall. The inboard and sketch plates are 6.35 mm thick, and annular plates are 16 mm thick