{"id":2108,"date":"2016-03-01T14:32:28","date_gmt":"2016-03-01T14:32:28","guid":{"rendered":"https:\/\/wldstainless.com\/?p=2108"},"modified":"2021-03-01T14:41:27","modified_gmt":"2021-03-01T14:41:27","slug":"why-does-stainless-steel-corrode","status":"publish","type":"post","link":"https:\/\/wldstainless.com\/cs\/why-does-stainless-steel-corrode\/","title":{"rendered":"Pro\u010d nerezov\u00e1 ocel koroduje?"},"content":{"rendered":"<p>Jak v\u0161ichni v\u00edme, <a href=\"https:\/\/wldstainless.com\/materials\/austenitic-stainless-steel\/304-304l-stainless-steel\/\">nerezov\u00e1 ocel<\/a> m\u00e1 schopnost odol\u00e1vat atmosf\u00e9rick\u00e9 oxidaci, to znamen\u00e1, \u017ee nebude rezav\u011bt, ale tak\u00e9 korodovat v m\u00e9diu, jako je kyselina, alk\u00e1lie a s\u016fl, to znamen\u00e1 odolnost proti korozi. Korozn\u00ed odolnost nerezov\u00e9 oceli je v\u0161ak podm\u00edn\u011bn\u00e1, to znamen\u00e1, \u017ee nerezov\u00e1 ocel v ur\u010dit\u00e9m m\u00e9diu je odoln\u00e1 v\u016f\u010di korozi, ale v jin\u00e9m m\u00e9diu m\u016f\u017ee b\u00fdt zni\u010dena. V souladu s t\u00edm \u017e\u00e1dn\u00e1 nerezov\u00e1 ocel nen\u00ed odoln\u00e1 v\u016f\u010di korozi ve v\u0161ech prost\u0159ed\u00edch.<\/p>\n<p>Nerezov\u00e1 ocel m\u016f\u017ee poskytnout vynikaj\u00edc\u00ed odolnost proti korozi v r\u016fzn\u00fdch pr\u016fmyslov\u00fdch odv\u011btv\u00edch, p\u0159\u00edsn\u011b vzato, vykazuj\u00ed vynikaj\u00edc\u00ed odolnost proti korozi ve v\u011bt\u0161in\u011b m\u00e9di\u00ed, ale u n\u011bkter\u00fdch m\u00e9di\u00ed je v\u00fdjime\u010dn\u00e1 kv\u016fli n\u00edzk\u00e9 chemick\u00e9 stabilit\u011b a korozi. Nerezov\u00e1 ocel proto nem\u016f\u017ee b\u00fdt odoln\u00e1 v\u016f\u010di v\u0161em m\u00e9di\u00edm krom\u011b mechanick\u00e9ho selh\u00e1n\u00ed. Koroze <a href=\"https:\/\/wldstainless.com\/materials\/austenitic-stainless-steel\/304-304l-stainless-steel\/\">nerezov\u00e1 ocel<\/a> se projevuje p\u0159edev\u0161\u00edm jako z\u00e1va\u017en\u00e1 forma koroze nerezov\u00e9 oceli je lok\u00e1ln\u00ed koroze (tj. korozn\u00ed prask\u00e1n\u00ed pod nap\u011bt\u00edm, d\u016flkov\u00e1 koroze, mezikrystalov\u00e1 koroze, korozn\u00ed \u00fanava a \u0161t\u011brbinov\u00e1 koroze). Tato lok\u00e1ln\u00ed koroze zp\u016fsobuje t\u00e9m\u011b\u0159 polovinu poruch. Abychom pochopili, pro\u010d nerezov\u00e1 ocel koroduje, mus\u00edme nejprve porozum\u011bt typu koroze nerezov\u00e9 oceli.<\/p>\n<p>&nbsp;<\/p>\n<p><strong><b>Korozn\u00ed prask\u00e1n\u00ed (SCC)<\/b><\/strong><\/p>\n<p>Korozn\u00ed prask\u00e1n\u00ed pod nap\u011bt\u00edm (SCC) je selh\u00e1n\u00ed nerezov\u00e9 oceli vystaven\u00e9 nam\u00e1h\u00e1n\u00ed v korozn\u00edm prost\u0159ed\u00ed v d\u016fsledku expanze siln\u00e9ho zrna. SCC m\u00e1 morfologii k\u0159ehk\u00e9ho lomu a m\u016f\u017ee se vyskytovat v materi\u00e1lech s vysokou hou\u017eevnatost\u00ed v p\u0159\u00edtomnosti tahov\u00e9ho nap\u011bt\u00ed (a\u0165 u\u017e zbytkov\u00e9ho nap\u011bt\u00ed nebo aplikovan\u00e9ho nap\u011bt\u00ed nebo oboj\u00edho) a korozivn\u00edch m\u00e9di\u00ed. V mikropohledu trhliny skrz zrno naz\u00fdvan\u00e9 transgranul\u00e1rn\u00ed trhliny a trhliny pod\u00e9l grafu expanze hranic zrn naz\u00fdvan\u00e9 intergranul\u00e1rn\u00ed trhlina, kdy\u017e se SCC roz\u0161\u00ed\u0159il do jedn\u00e9 hloubky (zat\u011b\u017eovac\u00ed nap\u011bt\u00ed na pr\u016f\u0159ezu materi\u00e1l\u016f, aby bylo dosa\u017eeno jeho lomov\u00e9ho nap\u011bt\u00ed) v vzduch, <a href=\"https:\/\/wldstainless.com\/materials\/austenitic-stainless-steel\/304-304l-stainless-steel\/\">nerezov\u00e1 ocel<\/a> jako norm\u00e1ln\u00ed trhlina (v tv\u00e1rn\u00e9m materi\u00e1lu, obvykle prost\u0159ednictv\u00edm mikroskopick\u00e9 agregace defekt\u016f) a rozpojen\u00ed.<\/p>\n<p>\u010c\u00e1st sou\u010d\u00e1sti, kter\u00e1 selhala v d\u016fsledku korozn\u00edho prask\u00e1n\u00ed pod nap\u011bt\u00edm, bude proto obsahovat oblasti charakterizovan\u00e9 korozn\u00edm prask\u00e1n\u00edm pod nap\u011bt\u00edm a oblasti \u201ed\u016flk\u016f\u201c spojen\u00e9 s polymerac\u00ed, kter\u00e1 byla m\u00edrn\u011b vadn\u00e1.<\/p>\n<p>&nbsp;<\/p>\n<p><strong>D\u016flkov\u00e1 koroze<\/strong><\/p>\n<p>D\u016flkov\u00e1 koroze ozna\u010duje nejv\u00edce nekorozivn\u00ed nebo rozpt\u00fdlenou m\u00edrnou lok\u00e1ln\u00ed korozi na povrchu kovov\u00fdch materi\u00e1l\u016f. Velikost spole\u010dn\u00e9ho d\u016flkov\u00e9ho bodu je men\u0161\u00ed ne\u017e 1,00 mm a hloubka je \u010dasto v\u011bt\u0161\u00ed ne\u017e povrchov\u00fd otvor, co\u017e m\u016f\u017ee b\u00fdt m\u011blk\u00fd d\u016flkov\u00fd d\u016flek nebo perforace.<\/p>\n<p>&nbsp;<\/p>\n<p><strong>Mezikrystalov\u00e1 koroze<\/strong><\/p>\n<p>Mezikrystalov\u00e1 koroze: Neuspo\u0159\u00e1dan\u00e1 dislokace zrn na hranici mezi r\u016fzn\u00fdmi zrny, a proto p\u0159\u00edzniv\u00e1 z\u00f3na pro segregaci rozpu\u0161t\u011bn\u00fdch prvk\u016f nebo precipitaci kovov\u00fdch slou\u010denin, jako jsou karbidy a \u03b4 f\u00e1ze v ocel\u00edch. Proto je u n\u011bkter\u00fdch korozivn\u00edch m\u00e9di\u00ed b\u011b\u017en\u00e9, \u017ee hranice zrn mohou b\u00fdt zkorodov\u00e1ny jako prvn\u00ed a v\u011bt\u0161ina kov\u016f a slitin m\u016f\u017ee v ur\u010dit\u00fdch korozivn\u00edch m\u00e9di\u00edch vykazovat mezikrystalovou korozi.<\/p>\n<p>&nbsp;<\/p>\n<p><strong>\u0160t\u011brbinov\u00e1 koroze<\/strong><\/p>\n<p>\u0160t\u011brbinov\u00e1 koroze ozna\u010duje v\u00fdskyt skvrnit\u00e9 koroze v prasklin\u00e1ch d\u00edl\u016f z nerezov\u00e9 oceli, co\u017e je druh m\u00edstn\u00ed koroze. M\u016f\u017ee se vyskytovat v trhlin\u00e1ch stagnace roztoku nebo na povrchu st\u00edn\u011bn\u00ed. Takov\u00e9 mezery se mohou tvo\u0159it na spoj\u00edch kov na kov nebo kov na nekov, nap\u0159\u00edklad na n\u00fdtech, \u0161roubech, t\u011bsn\u011bn\u00edch, ventilov\u00fdch sedlech a uvoln\u011bn\u00fdch povrchov\u00fdch usazenin\u00e1ch.<\/p>\n<p>&nbsp;<\/p>\n<p><strong>Obecn\u00e1 koroze<\/strong><\/p>\n<p>Rovnom\u011brn\u00e1 koroze na povrchu nerezov\u00e9 oceli. Nerezov\u00e9 oceli mohou vykazovat obecnou korozi v siln\u00fdch kyselin\u00e1ch a z\u00e1sad\u00e1ch. Kdy\u017e nastane obecn\u00e1 koroze, nerezov\u00e9 oceli se postupn\u011b zten\u010duj\u00ed a dokonce selh\u00e1vaj\u00ed, co\u017e nen\u00ed velk\u00fd probl\u00e9m, proto\u017ee takovou korozi lze obvykle p\u0159edv\u00eddat jednoduch\u00fdm ponorn\u00fdm testem. D\u00e1 se \u0159\u00edci, \u017ee nerezov\u00e1 ocel ozna\u010duje odolnost oceli v\u016f\u010di korozi v atmosf\u00e9\u0159e a slab\u00e9m korozn\u00edm m\u00e9diu, rychlost koroze je men\u0161\u00ed ne\u017e 0,01 mm\/rok, co\u017e je \u201ezcela odolnost proti korozi\u201c; Nerezov\u00e9 oceli s rychlost\u00ed koroze ni\u017e\u0161\u00ed ne\u017e 0,1 mm\/rok jsou pova\u017eov\u00e1ny za \u201eodoln\u00e9 proti korozi\u201c.<\/p>\n<p>&nbsp;<\/p>","protected":false},"excerpt":{"rendered":"<p>Jak v\u0161ichni v\u00edme, nerezov\u00e1 ocel m\u00e1 schopnost odol\u00e1vat atmosf\u00e9rick\u00e9 oxidaci, to znamen\u00e1, \u017ee nebude rezav\u011bt, ale tak\u00e9 korodovat v m\u00e9diu, jako je kyselina, z\u00e1sada a s\u016fl, to znamen\u00e1 odolnost proti korozi. Korozn\u00ed odolnost nerezov\u00e9 oceli je v\u0161ak podm\u00edn\u011bn\u00e1, to znamen\u00e1, \u017ee nerezov\u00e1 ocel v ur\u010dit\u00e9m m\u00e9diu je odoln\u00e1 proti korozi, ale v jin\u00e9m [\u2026]<\/p>","protected":false},"author":1,"featured_media":2110,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23],"tags":[],"class_list":["post-2108","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/wldstainless.com\/cs\/wp-json\/wp\/v2\/posts\/2108","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wldstainless.com\/cs\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wldstainless.com\/cs\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wldstainless.com\/cs\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/wldstainless.com\/cs\/wp-json\/wp\/v2\/comments?post=2108"}],"version-history":[{"count":4,"href":"https:\/\/wldstainless.com\/cs\/wp-json\/wp\/v2\/posts\/2108\/revisions"}],"predecessor-version":[{"id":2113,"href":"https:\/\/wldstainless.com\/cs\/wp-json\/wp\/v2\/posts\/2108\/revisions\/2113"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/wldstainless.com\/cs\/wp-json\/wp\/v2\/media\/2110"}],"wp:attachment":[{"href":"https:\/\/wldstainless.com\/cs\/wp-json\/wp\/v2\/media?parent=2108"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wldstainless.com\/cs\/wp-json\/wp\/v2\/categories?post=2108"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wldstainless.com\/cs\/wp-json\/wp\/v2\/tags?post=2108"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}