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(nai)腐蝕性(xing)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)(shi)主(zhu)要包括四(si)種(zhong)(zhong)方(fang)法，中(zhong)性(xing)鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)、銅(tong)鹽(yan)(yan)(yan)加速(su)醋(cu)酸(suan)(suan)(suan)鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)、醋(cu)酸(suan)(suan)(suan)鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)和(he)交(jiao)(jiao)變鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)。 中(zhong)性(xing)鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)，又(you)稱NSS試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)，是(shi)目前(qian)應用(yong)(yong)領(ling)域最(zui)廣(guang)、出現最(zui)早的(de)(de)一種(zhong)(zhong)加速(su)腐蝕(shi)(shi)試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)方(fang)法。一般采用(yong)(yong)5%的(de)(de)氯化(hua)(hua)鈉鹽(yan)(yan)(yan)水溶液(ye)，將溶液(ye)PH值調(diao)在(zai)中(zhong)性(xing)范圍(wei)(6.5～7.2)，作(zuo)為噴霧(wu)(wu)(wu)(wu)使用(yong)(yong)。試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)溫度(du)(du)控(kong)制在(zai)35℃，鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)的(de)(de)沉降率(lv)應為1～2ml/80cm/h。 銅(tong)鹽(yan)(yan)(yan)加速(su)醋(cu)酸(suan)(suan)(suan)鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)，又(you)稱CASS試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)，是(shi)近幾年(nian)發展(zhan)起(qi)來的(de)(de)一種(zhong)(zhong)快速(su)鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)腐蝕(shi)(shi)試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)。試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)溫度(du)(du)為50℃，鹽(yan)(yan)(yan)溶液(ye)中(zhong)加入(ru)少量(liang)銅(tong)鹽(yan)(yan)(yan)-氯化(hua)(hua)銅(tong)，具(ju)有強烈誘發腐蝕(shi)(shi)能力，腐蝕(shi)(shi)速(su)度(du)(du)是(shi)NSS試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)的(de)(de)8倍(bei)左(zuo)右。 醋(cu)酸(suan)(suan)(suan)鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)，又(you)稱ASS試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)，是(shi)建立在(zai)中(zhong)性(xing)鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)的(de)(de)基礎上發展(zhan)而來的(de)(de)。在(zai)5%氯化(hua)(hua)鈉溶液(ye)中(zhong)加入(ru)冰醋(cu)酸(suan)(suan)(suan)，將溶液(ye)的(de)(de)PH值降為3左(zuo)右，溶液(ye)變成酸(suan)(suan)(suan)性(xing)，最(zui)后形(xing)成的(de)(de)鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)也由中(zhong)性(xing)鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)變成酸(suan)(suan)(suan)性(xing)。其(qi)腐蝕(shi)(shi)速(su)度(du)(du)是(shi)NSS試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)的(de)(de)3倍(bei)左(zuo)右。 交(jiao)(jiao)變鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)則是(shi)屬于綜合鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)，它的(de)(de)原理是(shi)在(zai)中(zhong)性(xing)鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)的(de)(de)基礎上加恒定濕熱的(de)(de)試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)。主(zhu)要用(yong)(yong)于空(kong)腔型的(de)(de)整(zheng)機產(chan)(chan)品，通過潮濕環(huan)境(jing)的(de)(de)滲透，使鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)腐蝕(shi)(shi)既在(zai)產(chan)(chan)品表面發生(sheng)，也在(zai)產(chan)(chan)品內部發生(sheng)。交(jiao)(jiao)變鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)將產(chan)(chan)品環(huan)境(jing)在(zai)鹽(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)和(he)濕熱兩種(zhong)(zhong)條件下不斷(duan)替(ti)換(huan)，最(zui)后評估整(zheng)機產(chan)(chan)品的(de)(de)電性(xing)能和(he)機械性(xing)能的(de)(de)變化(hua)(hua)程度(du)(du)。