{"id":2535,"date":"2026-08-12T07:40:06","date_gmt":"2026-08-12T10:40:06","guid":{"rendered":"https:\/\/thermomac.com\/?p=2535"},"modified":"2026-08-12T07:40:08","modified_gmt":"2026-08-12T10:40:08","slug":"corrosion-bajo-aislamiento-el-enemigo-que-trabaja-donde-no-podes-mirar","status":"publish","type":"post","link":"https:\/\/thermomac.com\/en\/corrosion-bajo-aislamiento-el-enemigo-que-trabaja-donde-no-podes-mirar\/","title":{"rendered":"Corrosion under insulation: the enemy that works where you can't look"},"content":{"rendered":"

Refrigeration Insights Series. Season 2: The enemy within, part 4.<\/strong><\/p>\n\n\n\n

Myth: if the insulation looks good, the piping is fine.<\/p>\n\n\n\n

Reality: the most dangerous corrosion in your plant happens exactly on the other side of that impeccable jacketing, and it has been working for years without anyone seeing it.<\/p>\n\n\n\n

This week we take the myth apart with a 2008 IIAR technical paper written by two corrosion specialists: Patrick Dunn (Polyguard Products) and Richard Norsworthy (Lone Star Corrosion Services).<\/p>\n\n\n\n

The recipe for corrosion has four ingredients<\/h2>\n\n\n\n

The paper starts from first principles, and it is worth following along. For corrosion to occur, four elements are needed: an anode, a cathode, an electrical path connecting them (the metal itself) and an electrolyte.<\/p>\n\n\n\n

The key observation: three of the four elements are already present in every metal. The only one missing is the electrolyte. And what is an electrolyte in a refrigeration plant? Moisture. The moisture brought in by air condensing on cold surfaces, the moisture that enters through a damaged vapor barrier, the moisture trapped in wet thermal insulation.<\/p>\n\n\n\n

That is why corrosion under insulation (CUI) is so treacherous in refrigeration: our systems operate below ambient temperature, condensing moisture on every cold surface permanently. The insulation that was meant to protect the piping becomes, once wet, the sponge that keeps the electrolyte in contact with the metal 24 hours a day.<\/p>\n\n\n\n

The double damage of moisture<\/h2>\n\n\n\n

The paper points out an effect that usually goes unnoticed: moisture in the insulation not only enables corrosion, it also increases heat loss and degrades the insulation itself. In other words: while the piping corrodes in secret, the system also consumes more energy to hold the same temperature. Wet insulation charges you twice.<\/p>\n\n\n\n

The defense: layers, not patches<\/h2>\n\n\n\n

The strategy the authors propose is a layered defense system: well-executed vapor barriers, coatings applied to the metal before insulating, good-quality insulation materials, correct installation techniques and proper maintenance of the whole assembly.<\/p>\n\n\n\n

The order matters: the coating on the metal is the last line of defense once moisture has gotten past everything else. That is why the paper devotes its development to the selection, installation and proper use of coatings before the insulation is applied. What is done at that moment, with the piping bare, defines the next twenty years. It is no accident that IIAR 4 treats insulation as part of the installation, not as a finish: this paper explains why.<\/p>\n\n\n\n

Where to look first<\/h2>\n\n\n\n

CUI does not attack evenly. The critical points are the usual suspects: insulation terminations and end caps, support penetrations, valves and fittings where the vapor barrier is interrupted, outdoor runs, and anywhere the barrier looks damaged, sunken or with rust stains bleeding through the seams. That thread of rust showing through is the late symptom: by the time it can be seen from outside, it has been working inside for a long time.<\/p>\n\n\n\n

The practical takeaway<\/h2>\n\n\n\n

Add to your inspection rounds the points where the insulation is interrupted and look for three signs: a damaged vapor barrier, insulation that sounds or weighs different (wet), and rust stains at seams and terminations. When in doubt, opening an inspection window at the suspect point costs little; discovering a thinned pipe wall during a leak costs what you already know. And on your next project, demand the coating on the metal before the insulation: it is the cheapest insurance you will ever buy.<\/p>\n\n\n\n

Next week we continue with the corrosion family, in its most insidious version: stress corrosion cracking in ammonia vessels.<\/p>\n\n\n\n

Source: P. Dunn and R. Norsworthy, \u201cCorrosion Under Insulation of Equipment and Piping\u201d, Technical Paper #4, IIAR Ammonia Refrigeration Conference, 2008. Thermomac is an IIAR corporate member.<\/em><\/p>","protected":false},"excerpt":{"rendered":"

Serie Refrigeration Insights. Temporada 2: El enemigo interno, entrega 4. Mito: si el aislamiento se ve bien, la tuber\u00eda est\u00e1 bien. Realidad: la corrosi\u00f3n m\u00e1s peligrosa de tu planta ocurre exactamente del otro lado de esa chapa impecable, y lleva a\u00f1os trabajando sin que nadie la vea. Esta semana desarmamos el mito con un trabajo […]<\/p>\n","protected":false},"author":2,"featured_media":2536,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"set","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"_joinchat":[],"footnotes":""},"categories":[16],"tags":[],"class_list":["post-2535","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-refrigeration-insights"],"_links":{"self":[{"href":"https:\/\/thermomac.com\/en\/wp-json\/wp\/v2\/posts\/2535","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/thermomac.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/thermomac.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/thermomac.com\/en\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/thermomac.com\/en\/wp-json\/wp\/v2\/comments?post=2535"}],"version-history":[{"count":1,"href":"https:\/\/thermomac.com\/en\/wp-json\/wp\/v2\/posts\/2535\/revisions"}],"predecessor-version":[{"id":2537,"href":"https:\/\/thermomac.com\/en\/wp-json\/wp\/v2\/posts\/2535\/revisions\/2537"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/thermomac.com\/en\/wp-json\/wp\/v2\/media\/2536"}],"wp:attachment":[{"href":"https:\/\/thermomac.com\/en\/wp-json\/wp\/v2\/media?parent=2535"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/thermomac.com\/en\/wp-json\/wp\/v2\/categories?post=2535"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/thermomac.com\/en\/wp-json\/wp\/v2\/tags?post=2535"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}