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(fu)蝕性能，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)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)(wu)測試(shi)(shi)(shi)主(zhu)要(yao)包括四種(zhong)方(fang)法，中(zhong)性(xing)鹽(yan)(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)(wu)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)、銅鹽(yan)(yan)(yan)(yan)(yan)(yan)(yan)加(jia)速(su)(su)醋(cu)酸(suan)鹽(yan)(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)(wu)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)、醋(cu)酸(suan)鹽(yan)(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)(wu)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)和交變(bian)(bian)(bian)鹽(yan)(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)(wu)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)。 中(zhong)性(xing)鹽(yan)(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)(wu)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)，又稱NSS試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)，是(shi)(shi)目前應用(yong)領域最(zui)廣、出現最(zui)早的(de)(de)(de)(de)(de)一(yi)種(zhong)加(jia)速(su)(su)腐(fu)(fu)(fu)蝕(shi)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)方(fang)法。一(yi)般采用(yong)5%的(de)(de)(de)(de)(de)氯化(hua)(hua)鈉鹽(yan)(yan)(yan)(yan)(yan)(yan)(yan)水溶(rong)液(ye)，將溶(rong)液(ye)PH值(zhi)調在(zai)(zai)(zai)中(zhong)性(xing)范圍(6.5～7.2)，作為噴霧(wu)(wu)(wu)(wu)(wu)使用(yong)。試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)溫(wen)度(du)控制在(zai)(zai)(zai)35℃，鹽(yan)(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)(wu)的(de)(de)(de)(de)(de)沉(chen)降(jiang)率應為1～2ml/80cm/h。 銅鹽(yan)(yan)(yan)(yan)(yan)(yan)(yan)加(jia)速(su)(su)醋(cu)酸(suan)鹽(yan)(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)(wu)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)，又稱CASS試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)，是(shi)(shi)近(jin)幾年發(fa)(fa)展起來的(de)(de)(de)(de)(de)一(yi)種(zhong)快速(su)(su)鹽(yan)(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)(wu)腐(fu)(fu)(fu)蝕(shi)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)。試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)溫(wen)度(du)為50℃，鹽(yan)(yan)(yan)(yan)(yan)(yan)(yan)溶(rong)液(ye)中(zhong)加(jia)入(ru)少量(liang)銅鹽(yan)(yan)(yan)(yan)(yan)(yan)(yan)-氯化(hua)(hua)銅，具有強烈誘(you)發(fa)(fa)腐(fu)(fu)(fu)蝕(shi)能(neng)力，腐(fu)(fu)(fu)蝕(shi)速(su)(su)度(du)是(shi)(shi)NSS試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)的(de)(de)(de)(de)(de)8倍(bei)左右。 醋(cu)酸(suan)鹽(yan)(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)(wu)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)，又稱ASS試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)，是(shi)(shi)建立在(zai)(zai)(zai)中(zhong)性(xing)鹽(yan)(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)(wu)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)的(de)(de)(de)(de)(de)基礎上(shang)(shang)發(fa)(fa)展而來的(de)(de)(de)(de)(de)。在(zai)(zai)(zai)5%氯化(hua)(hua)鈉溶(rong)液(ye)中(zhong)加(jia)入(ru)冰醋(cu)酸(suan)，將溶(rong)液(ye)的(de)(de)(de)(de)(de)PH值(zhi)降(jiang)為3左右，溶(rong)液(ye)變(bian)(bian)(bian)成酸(suan)性(xing)，最(zui)后形成的(de)(de)(de)(de)(de)鹽(yan)(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)(wu)也(ye)由中(zhong)性(xing)鹽(yan)(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)(wu)變(bian)(bian)(bian)成酸(suan)性(xing)。其(qi)腐(fu)(fu)(fu)蝕(shi)速(su)(su)度(du)是(shi)(shi)NSS試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)的(de)(de)(de)(de)(de)3倍(bei)左右。 交變(bian)(bian)(bian)鹽(yan)(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)(wu)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)則是(shi)(shi)屬于(yu)綜(zong)合(he)鹽(yan)(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)(wu)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)，它的(de)(de)(de)(de)(de)原理是(shi)(shi)在(zai)(zai)(zai)中(zhong)性(xing)鹽(yan)(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)(wu)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)的(de)(de)(de)(de)(de)基礎上(shang)(shang)加(jia)恒定濕熱的(de)(de)(de)(de)(de)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)。主(zhu)要(yao)用(yong)于(yu)空(kong)腔型的(de)(de)(de)(de)(de)整機(ji)產(chan)品，通過潮濕環境(jing)的(de)(de)(de)(de)(de)滲(shen)透，使鹽(yan)(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)(wu)腐(fu)(fu)(fu)蝕(shi)既在(zai)(zai)(zai)產(chan)品表(biao)面發(fa)(fa)生，也(ye)在(zai)(zai)(zai)產(chan)品內部發(fa)(fa)生。交變(bian)(bian)(bian)鹽(yan)(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)(wu)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)將產(chan)品環境(jing)在(zai)(zai)(zai)鹽(yan)(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)(wu)和濕熱兩種(zhong)條(tiao)件下不斷替(ti)換，最(zui)后評估整機(ji)產(chan)品的(de)(de)(de)(de)(de)電性(xing)能(neng)和機(ji)械性(xing)能(neng)的(de)(de)(de)(de)(de)變(bian)(bian)(bian)化(hua)(hua)程度(du)。