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Research Opportunities in Corrosion Science and Engineering B Results of the Committee’s Corrosion Mitigation Questionnaire The committee’s questionnaire on mitigation of corrosion was released on March 10, 2009, for community input. Invitations were sent to key personnel at DOD, MTI, and LMI to distribute a link to the questionnaire. On April 1, 2009, the NACE Technical and Research Activities committee distributed the link to all members of NACE technical committees and the NACE Research committee. As of April 23, 2009, 172 respondents had started the survey, and 79 of them (45.9 percent) had completed the entire survey. The data gathered are summarized below.1 RESPONDENT INFORMATION Respondents described themselves as end users (39 percent), research and development personnel (31 percent), contractors (20 percent), and manufacturers (15 percent). Twenty-five percent of respondents described themselves as “other,” most of whom termed themselves “consultants.” The majority of respondents had been involved in corrosion mitigation for quite some time (67 percent for more than 15 years and 22 percent for 5 to 15 years) in diverse sectors including utilities, transportation, infrastructure, production and manufacturing, government, and health care. Sixty-seven percent valued their equipment or structures at greater than $10 million. The respondents indicated 1 As of October 21, 2009, 189 respondents had started the survey, and 90 (47.6 percent) had completed it. These new results are not included in the summary presented below. The data are available in the public access file at the National Academies.
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Research Opportunities in Corrosion Science and Engineering that they were responsible equipment in the following sectors: oil and gas exploration and production, transmission in pipelines, petroleum refining, chemical/petrochemical/pharmaceutical production, gas distribution, drinking water and sewer systems, and electric utilities. CORROSION ISSUES The questionnaire asked which forms of corrosion were of greatest importance or concern to the respondents. All forms of corrosion presented on the questionnaire as choices—general, pitting, crevice, microbially influenced corrosion, galvanic, erosion, and environmental cracking—were described as “sometimes an issue.” Pitting corrosion was most frequently described as “my biggest issues,” with general corrosion coming in second. Microbially influenced corrosion was most frequently described as “not an issue.” The consequence that most concerned the respondents was safety. Loss of production, environmental issues, and loss of use of the equipment were roughly tied for second place. Legal consequences were less frequently cited. Of those who cited “other,” “cost” was most frequently identified as the primary consequence. MITIGATION SYSTEMS This section of the questionnaire explored the types of mitigation systems currently being used by respondents. The most frequently selected options are shown in Table B.1 (respondents were allowed to select more than one). Respondents were also asked to say how frequently they used each technique. In other words, a respondent might have indicated that he or she used coupons (monitoring), external CP with coatings (electrochemical), and inhibitors such as those in water. In this question respondents were asked to say what percentage of their mitigation effort relied on a particular technique. Overall, external CP with coatings had the highest rate of use (35 percent), followed by materials selection based on environmental application (23 percent), organic barrier coatings (19 percent), corrosion inhibitors such as those used in water (19 percent), materials selection based on cost (18 percent), design of materials based on cost (16 percent), and sacrificial anodes (13 percent). Seventy-two percent of respondents said that they spent more than $200,000 per year on corrosion mitigation. An additional 13.5 percent spent between $50,000 and $200,000 per year.
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Research Opportunities in Corrosion Science and Engineering TABLE B.1 Types of Mitigation Systems Currently Being Used by Respondents Mitigation Technique General Type Total Number of Responses Most Frequently Cited Specific Techniques Number of Responses Monitoring Passive 108 Inspection 54 Coupons 18 Material selection Passive 103 Based on lifetime cost analysis 62 Based on environmental application 36 Electrochemical Active 91 External CP with coatings 57 Sacrificial anodes 18 Organic coatings Passive 79 Barrier 47 Combination 16 Inhibitors Passive 72 Those in water 47 Metallic coatings Passive 70 Flame sprayed 22 Sacrificial or barrier 15 Inorganic coatings Passive 63 High temperature 24 Low temperature 21 EFFECTIVENESS OF MITIGATION SYSTEMS This section of the questionnaire attempted to assess respondents’ overall satisfaction with the various mitigation techniques employed. Respondents ranked the various techniques on a scale from 1 to 5 (1 = not satisfied at all, 3 = moderately satisfied, 5 = completely satisfied). Overall, respondents were at least moderately satisfied with the mitigation techniques they used. Active, externally applied CP with coatings had the highest average satisfaction ranking at 4.22. Hybrid organic/inorganic coatings—plasma electrolytic had the lowest average satisfaction ranking at 2.60. The highest-ranked techniques, in terms of overall satisfaction, are shown in Table B.2, and. the lowest-ranked techniques, in terms of overall satisfaction, are shown in Table B.3. Ninety-nine responses were received on the specific difficulties encountered with various techniques (questions 14 and 15 of the questionnaire give details). An informal review of respondents’ answers showed that the considerations listed in Table B.4 seemed to be of general concern.
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Research Opportunities in Corrosion Science and Engineering TABLE B.2 Highest-Ranked Techniques, in Terms of Overall Satisfaction Technique Average Ranking Number of Responses Externally applied CP with coatings 4.22 57 Material selection—other 4.07 15 Materials selection based on environmental application 4.00 40 Sacrificial anodes 3.98 50 Design of materials based on cost 3.97 38 Materials selection based on cost 3.90 49 TABLE B.3 Lowest-Ranked Techniques, in Terms of Overall Satisfaction Technique Average Ranking Number of Responses Hybrid organic/inorganic coatings—plasma electrolytic 2.60 5 Active sensors—automatic 2.91 11 Inorganic coatings—special layered organics 2.92 12 TABLE B.4 Considerations of Greatest Concern to Respondents General Consideration Specific Applications or Issues Monitoring For high-temperature applications For measuring (with sensors) localized corrosion Unreliability For underdeposit corrosion For stress corrosion cracking Remote sensing Access to information Materials database with updated costs Suitability of various materials in different environments Chemical inhibitors—their use and efficacy (debunking of the proprietary “cocktails”) Coatings Surface preparation Protection under disbonded coatings Cathodic protection Insufficient training or knowledge of operators Prediction Prediction of lifetime Prediction of actual conditions Prediction of damage mechanisms
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Research Opportunities in Corrosion Science and Engineering IDEALIZED OR STATE-OF-THE-ART MITIGATION SYSTEMS This section of the questionnaire addressed current state-of-the-art technologies in corrosion mitigation. Sixty-six respondents described the current state-of-the-art mitigation system for their application, with many citing a combination of methods. Active protection (cathodic or anodic), materials selection, and coatings/claddings were the most frequently cited techniques. Cathodic protection was often listed in combination with coatings. Chemistry/inhibitors/process control was next most frequently cited technique followed by sensors. Remote monitoring, modeling, pigging, and inspection were mentioned only one or two times each. Sixty-four percent of those who responded said they used the state of the art, 24 percent said they used it in some instances, 3 percent did not use it, and the remainder, generally self-described as consultants, did not use the technologies at all. For those who used the state of the art, the most frequently given reason was that it worked and was either inexpensive or cost-effective. ADVANCES IN MITIGATION Having had an opportunity to consider the types of mitigation systems available, the efficacy of those currently used, and the state-of-the-art technologies available, respondents were asked suggest scientific advances that would contribute to the development of new and/or better mitigation technologies. The majority (63 percent) of respondents thought that future research should include both fundamental and applied sciences, with some commenting that the balance should tilt toward applied research. Twenty-five percent felt that future research should be applied, and the rest were divided between fundamental and “don’t know.” When asked where future research should focus specifically to enable advances that would help to develop new and/or better mitigation technologies, the top three areas were monitoring (50 percent), coatings (45 percent), and active systems (41 percent) (more than one option could be selected). Others suggested sensors (29 percent), passive systems (21 percent), and “other” (21 percent). Improvement in mitigation system lifetime and improvement in the costs of mitigation ranked the lowest (14 percent and 12 percent, respectively). In the area of monitoring, the majority of the suggestions favored improved remote modeling or better sensors and a method of monitoring or measuring localized (pitting) corrosion. Improved inspection methods (nondestructive and/or not requiring shutting down facilities) and improved costs were also mentioned. With respect to coatings, the most frequently suggested improvements related to better
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Research Opportunities in Corrosion Science and Engineering high-temperature performance and less need for surface preparation (answers to question 20 of the questionnaire give details). Respondents were also asked to craft questions they would like to see answered by future research in this field (questions 22 and 23 give details). Common themes included modeling (predicting lifetimes, modeling environments and new alloys, extrapolating the results of short-term testing to long-term performance), and monitoring or assessing localized corrosion, including pitting and microbially influenced corrosion.