產品長期暴露在空氣中，在自然條件的作用下，可能導致材料或性能被破壞或變質，這是自然的腐蝕效果。發生腐蝕的原因往往和環境中的氧氣、溫濕度、污染物等腐蝕成分有關。其中，鹽霧腐蝕就是最常見且破壞力很大的腐蝕。 鹽霧測試的作用 鹽霧是如何腐蝕金屬材料的?這是因為鹽霧中含有氯離子，可以穿透金屬表面的氧化層和防護層，直接與金屬層發生電化學反應，引起腐蝕。而且氯離子含有一定的水合能，很容易被金屬表面的空隙吸附，并取代氧化層中的氧，把不溶的氧化物變成可溶的氯化物，使本來具有防護性能的表面層變得活潑。 既然產品可能會受到鹽霧的腐蝕，那么在出廠前，就需要評估其耐腐蝕(shi)性能，評價其使用壽命。 鹽霧測試的種類 鹽霧測試可以采用天然環境暴露或人工加速模擬鹽霧環境進行試驗。天然環境暴露是最接近真實使用情況的方法，但缺點是試驗時間太長，可能廠家無法承受其時間成本。而人工加速模擬鹽霧環境試驗則是利用鹽霧試驗箱，將產品放置于試驗箱中，模擬鹽霧環境對產品的耐鹽霧腐蝕性能進行考核。 與天然環境相比較，人工鹽霧測試可以控制鹽霧濃度，使腐蝕速度大大提高，縮短試驗時間。以目前的技術條件來說，天然環境中需要測試一年以上的產品，在人工模擬鹽霧環境條件下，只要24小時即可得到接近的效果。

  鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)測(ce)試(shi)(shi)(shi)(shi)主要(yao)包括四種方法，中(zhong)(zhong)性(xing)(xing)(xing)鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)、銅鹽(yan)(yan)(yan)加(jia)速醋(cu)酸(suan)(suan)(suan)鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)、醋(cu)酸(suan)(suan)(suan)鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)和交變鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)。 中(zhong)(zhong)性(xing)(xing)(xing)鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)，又稱NSS試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)，是(shi)(shi)目前應用(yong)領域(yu)最(zui)廣、出(chu)現最(zui)早的(de)(de)(de)一(yi)種加(jia)速腐(fu)(fu)(fu)蝕(shi)(shi)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)方法。一(yi)般采用(yong)5%的(de)(de)(de)氯化鈉鹽(yan)(yan)(yan)水溶(rong)(rong)液(ye)(ye)，將(jiang)(jiang)溶(rong)(rong)液(ye)(ye)PH值調在(zai)(zai)(zai)(zai)中(zhong)(zhong)性(xing)(xing)(xing)范圍(wei)(6.5～7.2)，作為噴霧(wu)(wu)(wu)(wu)使用(yong)。試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)溫度(du)控制(zhi)在(zai)(zai)(zai)(zai)35℃，鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)的(de)(de)(de)沉降率應為1～2ml/80cm/h。 銅鹽(yan)(yan)(yan)加(jia)速醋(cu)酸(suan)(suan)(suan)鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)，又稱CASS試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)，是(shi)(shi)近幾年發(fa)(fa)(fa)展起(qi)來的(de)(de)(de)一(yi)種快速鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)腐(fu)(fu)(fu)蝕(shi)(shi)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)。試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)溫度(du)為50℃，鹽(yan)(yan)(yan)溶(rong)(rong)液(ye)(ye)中(zhong)(zhong)加(jia)入(ru)少量銅鹽(yan)(yan)(yan)-氯化銅，具有強烈誘發(fa)(fa)(fa)腐(fu)(fu)(fu)蝕(shi)(shi)能(neng)力，腐(fu)(fu)(fu)蝕(shi)(shi)速度(du)是(shi)(shi)NSS試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)的(de)(de)(de)8倍左右。 醋(cu)酸(suan)(suan)(suan)鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)，又稱ASS試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)，是(shi)(shi)建立(li)在(zai)(zai)(zai)(zai)中(zhong)(zhong)性(xing)(xing)(xing)鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)的(de)(de)(de)基礎(chu)上發(fa)(fa)(fa)展而來的(de)(de)(de)。在(zai)(zai)(zai)(zai)5%氯化鈉溶(rong)(rong)液(ye)(ye)中(zhong)(zhong)加(jia)入(ru)冰醋(cu)酸(suan)(suan)(suan)，將(jiang)(jiang)溶(rong)(rong)液(ye)(ye)的(de)(de)(de)PH值降為3左右，溶(rong)(rong)液(ye)(ye)變成(cheng)酸(suan)(suan)(suan)性(xing)(xing)(xing)，最(zui)后形成(cheng)的(de)(de)(de)鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)也(ye)由中(zhong)(zhong)性(xing)(xing)(xing)鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)變成(cheng)酸(suan)(suan)(suan)性(xing)(xing)(xing)。其(qi)腐(fu)(fu)(fu)蝕(shi)(shi)速度(du)是(shi)(shi)NSS試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)的(de)(de)(de)3倍左右。 交變鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)則(ze)是(shi)(shi)屬于綜合鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)，它的(de)(de)(de)原理是(shi)(shi)在(zai)(zai)(zai)(zai)中(zhong)(zhong)性(xing)(xing)(xing)鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)的(de)(de)(de)基礎(chu)上加(jia)恒定(ding)濕(shi)(shi)熱(re)(re)的(de)(de)(de)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)。主要(yao)用(yong)于空腔型的(de)(de)(de)整機產(chan)(chan)品(pin)(pin)，通過(guo)潮濕(shi)(shi)環(huan)境(jing)(jing)的(de)(de)(de)滲透(tou)，使鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)腐(fu)(fu)(fu)蝕(shi)(shi)既在(zai)(zai)(zai)(zai)產(chan)(chan)品(pin)(pin)表面發(fa)(fa)(fa)生(sheng)，也(ye)在(zai)(zai)(zai)(zai)產(chan)(chan)品(pin)(pin)內部(bu)發(fa)(fa)(fa)生(sheng)。交變鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)將(jiang)(jiang)產(chan)(chan)品(pin)(pin)環(huan)境(jing)(jing)在(zai)(zai)(zai)(zai)鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)和濕(shi)(shi)熱(re)(re)兩種條件下不斷替換，最(zui)后評估(gu)整機產(chan)(chan)品(pin)(pin)的(de)(de)(de)電性(xing)(xing)(xing)能(neng)和機械性(xing)(xing)(xing)能(neng)的(de)(de)(de)變化程度(du)。