{"id":1367,"date":"2024-11-26T14:26:38","date_gmt":"2024-11-26T06:26:38","guid":{"rendered":"https:\/\/www.tflequip.com\/?p=1367"},"modified":"2024-11-26T14:26:38","modified_gmt":"2024-11-26T06:26:38","slug":"why-does-stainless-steel-rust-and-corrode","status":"publish","type":"post","link":"https:\/\/www.tflequip.com\/cs\/why-does-stainless-steel-rust-and-corrode\/","title":{"rendered":"Pro\u010d nerezov\u00e1 ocel rezav\u00ed a koroduje?"},"content":{"rendered":"

Pro\u010d nerezov\u00e1 ocel koroduje a rezav\u00ed? Kdy\u017e se na povrchu nerezov\u00e9 oceli objev\u00ed hn\u011bd\u00e9 rezav\u00e9 skvrny (te\u010dky), lid\u00e9 jsou velmi p\u0159ekvapeni: mysl\u00ed si, \u017ee nerezov\u00e1 ocel nekoroduje a nerezav\u00ed, a pokud koroduje a rezav\u00ed, nen\u00ed to nerezov\u00e1 ocel a v\u011bt\u0161ina oceli m\u00e1 probl\u00e9my. Ve skute\u010dnosti se jedn\u00e1 o jednostrann\u00fd a nespr\u00e1vn\u00fd n\u00e1zor, kter\u00fd postr\u00e1d\u00e1 pochopen\u00ed nerezov\u00e9 oceli. Nerezov\u00e1 ocel za ur\u010dit\u00fdch podm\u00ednek tak\u00e9 koroduje a rezav\u00ed.<\/p>\n

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1. Nerezov\u00e1 ocel bude za odpov\u00eddaj\u00edc\u00edch podm\u00ednek rovn\u011b\u017e korodovat.<\/p>\n

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Sc\u00e9n\u00e1\u0159e pou\u017eit\u00ed nerezov\u00e9 oceli jsou velmi slo\u017eit\u00e9 a jedin\u00e1 pasiva\u010dn\u00ed vrstva oxidu chromu nem\u016f\u017ee splnit po\u017eadavky na vysokou odolnost proti korozi. Proto se podle rozd\u00edl\u016f v rozsahu pou\u017eit\u00ed mus\u00ed do oceli p\u0159id\u00e1vat prvky, jako je molybden (Mo), m\u011b\u010f (Cu) a dus\u00edk (N), aby se zlep\u0161ilo slo\u017een\u00ed pasiva\u010dn\u00edho filmu a d\u00e1le se zlep\u0161ila korozn\u00ed odolnost nerezov\u00e9 oceli. P\u0159id\u00e1n\u00edm Mo se vzhledem k tomu, \u017ee produkt koroze MoO2- je bl\u00edzko matrice a prudce podporuje pasivaci matrice, zabra\u0148uje korozi matrice; p\u0159id\u00e1n\u00edm Cu se pasiva\u010dn\u00ed film na povrchu nerezov\u00e9 oceli st\u00e1v\u00e1 CuCl, proto\u017ee nereaguje s korozivn\u00edmi l\u00e1tkami a zlep\u0161uje korozn\u00ed odolnost; p\u0159id\u00e1n\u00edm N se vzhledem k tomu, \u017ee pasiva\u010dn\u00ed film je obohacen o Cr2N, zvy\u0161uje koncentrace Cr v pasiva\u010dn\u00edm filmu, tak\u017ee se zlep\u0161uje korozn\u00ed odolnost nerezov\u00e9 oceli.<\/p>\n

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Odolnost nerezov\u00e9 oceli proti korozi je podm\u00edn\u011bn\u00e1. Ur\u010dit\u00e1 t\u0159\u00edda nerezov\u00e9 oceli je odoln\u00e1 proti korozi v ur\u010dit\u00e9m prost\u0159ed\u00ed, ale v jin\u00e9m prost\u0159ed\u00ed se po\u0161kod\u00ed. Z\u00e1rove\u0148 je korozn\u00ed odolnost nerezov\u00e9 oceli tak\u00e9 relativn\u00ed. Zat\u00edm neexistuje nerezov\u00e1 ocel, kter\u00e1 by nikdy nekorodovala ve v\u0161ech prost\u0159ed\u00edch.<\/p>\n

\".jpg\"<\/p>\n

2. Nerezov\u00e1 ocel nem\u016f\u017ee korodovat a reziv\u011bt.<\/p>\n

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Na povrchu se rovn\u011b\u017e vytvo\u0159\u00ed oxid. D\u016fvodem, pro\u010d jsou v\u0161echny nerezov\u00e9 materi\u00e1ly na trhu nerezov\u00e9, je p\u0159\u00edtomnost prvku Cr. Hlavn\u00edm d\u016fvodem (principem) korozn\u00ed odolnosti nerezov\u00e9 oceli je koncept pasiva\u010dn\u00edho filmu. Zjednodu\u0161en\u011b \u0159e\u010deno, pasiva\u010dn\u00ed film je film slo\u017een\u00fd p\u0159ev\u00e1\u017en\u011b z Cr2O3 pokr\u00fdvaj\u00edc\u00ed povrch nerezov\u00e9ho materi\u00e1lu. D\u00edky v\u00fdskytu tohoto filmu je omezena koroze matrice z korozivzdorn\u00e9 oceli v r\u016fzn\u00fdch m\u00e9di\u00edch. Tato situace se naz\u00fdv\u00e1 pasivace. Existuj\u00ed dv\u011b situace vzniku tohoto typu pasiva\u010dn\u00edho filmu. Jednou z nich je, \u017ee nerezov\u00e1 ocel m\u00e1 sama o sob\u011b schopnost samopasivace. Tato samopasiva\u010dn\u00ed schopnost se zrychluje se zvy\u0161uj\u00edc\u00edm se obsahem chromu, tak\u017ee m\u00e1 odolnost proti korozi; druhou \u010dast\u011bj\u0161\u00ed v\u00fdrobn\u00ed podm\u00ednkou je, \u017ee nerezov\u00e1 ocel vytv\u00e1\u0159\u00ed pasiva\u010dn\u00ed film v procesu koroze v r\u016fzn\u00fdch vodn\u00fdch roztoc\u00edch (elektrolytech), \u010d\u00edm\u017e omezuje korozi. P\u0159i po\u0161kozen\u00ed pasiva\u010dn\u00edho filmu se m\u016f\u017ee okam\u017eit\u011b vytvo\u0159it nov\u00fd pasiva\u010dn\u00ed film.<\/p>\n

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Existuj\u00ed t\u0159i d\u016fvody, pro\u010d m\u00e1 pasiva\u010dn\u00ed vrstva z nerezov\u00e9 oceli schopnost odol\u00e1vat korozi: za prv\u00e9, tlou\u0161\u0165ka pasiva\u010dn\u00ed vrstvy je velmi tenk\u00e1, co\u017e m\u016f\u017ee b\u00fdt v prost\u0159ed\u00ed s obsahem chromu >10 jen n\u011bkolik mikron\u016f.5%; za druh\u00e9, m\u011brn\u00e1 hmotnost pasiva\u010dn\u00ed vrstvy je v\u011bt\u0161\u00ed ne\u017e m\u011brn\u00e1 hmotnost substr\u00e1tu; tyto dv\u011b vlastnosti nazna\u010duj\u00ed, \u017ee pasiva\u010dn\u00ed vrstva je tenk\u00e1 a z\u00e1rove\u0148 hust\u00e1, tak\u017ee je obt\u00ed\u017en\u00e9, aby pasiva\u010dn\u00ed vrstvou proniklo korozn\u00ed prost\u0159ed\u00ed a rychle zkorodovalo substr\u00e1t; t\u0159et\u00ed vlastnost\u00ed je, \u017ee koncentrace chromu v pasiva\u010dn\u00ed vrstv\u011b je v\u00edce ne\u017e t\u0159ikr\u00e1t vy\u0161\u0161\u00ed ne\u017e v substr\u00e1tu; pasiva\u010dn\u00ed vrstva m\u00e1 tedy vysokou odolnost proti korozi.<\/p>\n

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Nerezov\u00e1 ocel m\u00e1 schopnost odol\u00e1vat atmosf\u00e9rick\u00e9 oxidaci, tj. nerezav\u00ed, a m\u00e1 tak\u00e9 schopnost nekorodovat v prost\u0159ed\u00edch obsahuj\u00edc\u00edch kyseliny, z\u00e1sady a soli, tj. odolnost proti korozi. Jej\u00ed korozn\u00ed odolnost se v\u0161ak li\u0161\u00ed v z\u00e1vislosti na chemick\u00e9m slo\u017een\u00ed samotn\u00e9 oceli, stavu ochrany, rozsahu pou\u017eit\u00ed a druhu prost\u0159ed\u00ed. Nap\u0159\u00edklad ocelov\u00e9 trubky 304 maj\u00ed relativn\u011b dobrou odolnost proti korozi v such\u00e9m a \u010dist\u00e9m prost\u0159ed\u00ed, ale kdy\u017e se p\u0159em\u00edst\u00ed do pob\u0159e\u017en\u00edch oblast\u00ed, v mo\u0159sk\u00e9 mlze obsahuj\u00edc\u00ed v\u011bt\u0161\u00ed mno\u017estv\u00ed soli rychle zreziv\u00ed; zat\u00edmco ocelov\u00e9 trubky 316 si vedou dob\u0159e. Ne v\u0161echny nerezov\u00e9 oceli jsou tedy odoln\u00e9 proti korozi a nerezav\u00ed ve v\u0161ech prost\u0159ed\u00edch.<\/p>","protected":false},"excerpt":{"rendered":"

Why does stainless steel corrode and rust? When brown rust spots (dots) appear on the surface of stainless steel, people are very surprised: they think that stainless steel will not corrode and rust, and if it corrodes and rusts, it is not stainless steel, and most of the steel has problems. In fact, this is […]<\/p>","protected":false},"author":4,"featured_media":1368,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[36],"tags":[],"acf":[],"_links":{"self":[{"href":"https:\/\/www.tflequip.com\/cs\/wp-json\/wp\/v2\/posts\/1367"}],"collection":[{"href":"https:\/\/www.tflequip.com\/cs\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.tflequip.com\/cs\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.tflequip.com\/cs\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/www.tflequip.com\/cs\/wp-json\/wp\/v2\/comments?post=1367"}],"version-history":[{"count":0,"href":"https:\/\/www.tflequip.com\/cs\/wp-json\/wp\/v2\/posts\/1367\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.tflequip.com\/cs\/wp-json\/wp\/v2\/media\/1368"}],"wp:attachment":[{"href":"https:\/\/www.tflequip.com\/cs\/wp-json\/wp\/v2\/media?parent=1367"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.tflequip.com\/cs\/wp-json\/wp\/v2\/categories?post=1367"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.tflequip.com\/cs\/wp-json\/wp\/v2\/tags?post=1367"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}