{"id":7237,"date":"2006-11-01T00:00:00","date_gmt":"2006-11-01T00:00:00","guid":{"rendered":"https:\/\/insulation.org\/io\/articles\/once-upon-a-time-a-corrosion-fairy-tale\/"},"modified":"2006-11-01T00:00:00","modified_gmt":"2006-11-01T00:00:00","slug":"once-upon-a-time-a-corrosion-fairy-tale","status":"publish","type":"articles","link":"https:\/\/insulation.org\/io\/articles\/once-upon-a-time-a-corrosion-fairy-tale\/","title":{"rendered":"Once Upon a Time &hellip; A Corrosion Fairy Tale"},"content":{"rendered":"<p>This issue of <em>Insulation  Outlook<\/em> is focusing on corrosion under insulation (please feel free to  check the front cover to see if I should have stopped to ask for directions).  Fortunately, corrosion only occurs under insulation once every 3 or 4 years,  because it can be a considerable threat to structural integrity. I just happen  to be a corrosion engineer. (And that merely acknowledges the sequence of  chance events that brought this about&mdash;relatively few of my colleagues always dreamed  of being corrosion engineers. I wonder how many of you, when you were a  5-year-old future firefighter or cowboy, would have punctuated career day at  school with, &ldquo;Insulation is where it&rsquo;s at!&rdquo;)<\/p>\n<p>I&rsquo;m also a longtime member of The National Association of  Corrosion Engineers (NACE) International&mdash;The Corrosion Society, and have  contributed more or less monthly columns to the society&rsquo;s principal periodical  for more than 5 years now. That is, until I tested positive for steroids. (I  never knowingly took steroids&mdash;honestly, I thought it was morphine&mdash;though I have experienced  some conspicuous muscular development that has unexpectedly improved my  competitive eyebrow-raising skills).<\/p>\n<p>This would seem an appropriate time to mention that nothing  contained in this article should be construed as an official statement on  behalf of NACE, NIA, my company, or your company&mdash;I&rsquo;m not even sure I&rsquo;m speaking for  myself.<\/p>\n<p>It is noteworthy that NACE&rsquo;s technical committees are  readopting Publication 10A392, &ldquo;Effectiveness of Cathodic Protection on  Thermally Insulated Underground Metallic Structures.&rdquo; It is not necessarily a  coincidence that this roughly corresponds to the <br \/>\n  25th anniversary of the most significant advance in the  prevailing approach to corrosion control for these structures: the use of  barrier coatings on structure surfaces prior to the placement of insulation.<\/p>\n<p>Paraphrased in a nutshell (how fitting), here are the four <br \/>\n  general approaches to corrosion control:<\/p>\n<ul>\n<ul>\n<li>Material  selection&mdash;especially the use of components that resist corrosion in  specific environments<\/li>\n<li>Inhibitors  that reduce the corrosiveness of the environment, typically inside a tank  or piping system<\/li>\n<li>Coatings  and linings, typically with dielectric properties intended to isolate  surfaces from corrosive environments<\/li>\n<li>Cathodic  protection (CP)<\/li>\n<\/ul>\n<\/ul>\n<p>CP has been variously defined, but one view is that metal  loss (the main reason for all the fuss about corrosion) happens when current  leaves a buried or submerged surface at anodic sites in the form of  electrically charged metal ions; CP attempts to minimize this discharge by  applying an external current to the entire structure surface. This makes all  sites cathodic. Reduced current discharge means reduced corrosion.<\/p>\n<h5>Once Upon a Time<\/h5>\n<p>Once upon a time (before some of today&rsquo;s best practices were  in common use), in the magical land of the northern Midwest, there was a  direct-buried steam-piping system with fiberglass thermal insulation in half  shells and a thin outer moisture barrier of galvanized steel&mdash;hardly the best choice for direct burial. The  real problem, though, was underestimating the effectiveness of the insulation  in preventing heat loss to the environment, which might have avoided winter  soil stresses. Instead, the ground froze (and expanded), the outer shell was  crushed, and the spring thaw brought oxygenated water into contact with the  pipe steel at joints and voids.<\/p>\n<p>An external CP system had been installed, but current  distribution is essentially linear. And CP current actually promotes moisture  migration. When the water migrated along under the insulation, adequate  protective current could not reach all of the corroding sites. The same conditions  limited the ability to identify active corrosion with traditional test methods  for CP evaluation. The resulting failures were basically consistent with the  fundamental conclusion of 10A392: &ldquo;Generally, the application of external CP to  thermally insulated metallic surfaces has been ineffective.&rdquo;<\/p>\n<p>Surface coatings are much more successful in conjunction  with a nonmetallic external jacket as a moisture barrier. The established  developments in coatings and linings, material selection, and construction  practices, along with evaluation techniques like internal pipeline inspection  tools, make it possible to use the advantages of thermal insulation for  underground metallic structures. And that greatly reduces the risk of corrosion  failures, so we can all live happily ever after.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>This issue of Insulation Outlook is focusing on corrosion under insulation (please feel free to check the front cover to see if I should have stopped to ask for directions). Fortunately, corrosion only occurs under insulation once every 3 or 4 years, because it can be a considerable threat to structural integrity. I just happen<\/p>\n","protected":false},"author":[155],"featured_media":0,"template":"","categories":[26],"class_list":["post-7237","articles","type-articles","status-publish","hentry","category-corrosion","author-norm-moriber"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v24.0 (Yoast SEO v24.6) - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Once Upon a Time &hellip; A Corrosion Fairy Tale - Insulation Outlook Magazine<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/insulation.org\/io\/articles\/once-upon-a-time-a-corrosion-fairy-tale\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Once Upon a Time &hellip; A Corrosion Fairy Tale\" \/>\n<meta property=\"og:description\" content=\"This issue of Insulation Outlook is focusing on corrosion under insulation (please feel free to check the front cover to see if I should have stopped to ask for directions). 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