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)(yan)(yan)霧(wu)(wu)(wu)(wu)測試(shi)(shi)(shi)(shi)主要包括四種方法(fa)，中(zhong)(zhong)(zhong)性(xing)(xing)鹽(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)(yan)、銅(tong)鹽(yan)(yan)(yan)(yan)(yan)加(jia)速醋(cu)酸鹽(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)(yan)、醋(cu)酸鹽(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)(yan)和(he)交(jiao)變(bian)鹽(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)(yan)。 中(zhong)(zhong)(zhong)性(xing)(xing)鹽(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)(yan)，又(you)稱NSS試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)(yan)，是(shi)目(mu)前應用領域最廣(guang)、出現最早的(de)(de)一(yi)種加(jia)速腐(fu)(fu)蝕(shi)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)(yan)方法(fa)。一(yi)般(ban)采用5%的(de)(de)氯化鈉(na)鹽(yan)(yan)(yan)(yan)(yan)水溶(rong)液(ye)，將(jiang)溶(rong)液(ye)PH值調在(zai)(zai)(zai)中(zhong)(zhong)(zhong)性(xing)(xing)范圍(6.5～7.2)，作(zuo)為(wei)噴霧(wu)(wu)(wu)(wu)使用。試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)(yan)溫度(du)(du)控制在(zai)(zai)(zai)35℃，鹽(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)的(de)(de)沉降(jiang)(jiang)率應為(wei)1～2ml/80cm/h。 銅(tong)鹽(yan)(yan)(yan)(yan)(yan)加(jia)速醋(cu)酸鹽(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)(yan)，又(you)稱CASS試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)(yan)，是(shi)近(jin)幾(ji)年發(fa)展(zhan)(zhan)起來(lai)(lai)的(de)(de)一(yi)種快速鹽(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)腐(fu)(fu)蝕(shi)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)(yan)。試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)(yan)溫度(du)(du)為(wei)50℃，鹽(yan)(yan)(yan)(yan)(yan)溶(rong)液(ye)中(zhong)(zhong)(zhong)加(jia)入少量(liang)銅(tong)鹽(yan)(yan)(yan)(yan)(yan)-氯化銅(tong)，具有強烈誘(you)發(fa)腐(fu)(fu)蝕(shi)能力，腐(fu)(fu)蝕(shi)速度(du)(du)是(shi)NSS試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)(yan)的(de)(de)8倍左右。 醋(cu)酸鹽(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)(yan)，又(you)稱ASS試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)(yan)，是(shi)建立(li)在(zai)(zai)(zai)中(zhong)(zhong)(zhong)性(xing)(xing)鹽(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)(yan)的(de)(de)基礎上發(fa)展(zhan)(zhan)而來(lai)(lai)的(de)(de)。在(zai)(zai)(zai)5%氯化鈉(na)溶(rong)液(ye)中(zhong)(zhong)(zhong)加(jia)入冰醋(cu)酸，將(jiang)溶(rong)液(ye)的(de)(de)PH值降(jiang)(jiang)為(wei)3左右，溶(rong)液(ye)變(bian)成酸性(xing)(xing)，最后形成的(de)(de)鹽(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)也(ye)由中(zhong)(zhong)(zhong)性(xing)(xing)鹽(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)變(bian)成酸性(xing)(xing)。其腐(fu)(fu)蝕(shi)速度(du)(du)是(shi)NSS試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)(yan)的(de)(de)3倍左右。 交(jiao)變(bian)鹽(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)(yan)則是(shi)屬于綜合鹽(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)(yan)，它的(de)(de)原理是(shi)在(zai)(zai)(zai)中(zhong)(zhong)(zhong)性(xing)(xing)鹽(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)(yan)的(de)(de)基礎上加(jia)恒(heng)定濕熱的(de)(de)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)(yan)。主要用于空腔(qiang)型(xing)的(de)(de)整機產品(pin)，通過潮濕環(huan)境的(de)(de)滲透，使鹽(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)腐(fu)(fu)蝕(shi)既在(zai)(zai)(zai)產品(pin)表(biao)面發(fa)生，也(ye)在(zai)(zai)(zai)產品(pin)內部發(fa)生。交(jiao)變(bian)鹽(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)(yan)(yan)(yan)將(jiang)產品(pin)環(huan)境在(zai)(zai)(zai)鹽(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)和(he)濕熱兩種條件下不斷(duan)替換，最后評(ping)估整機產品(pin)的(de)(de)電性(xing)(xing)能和(he)機械性(xing)(xing)能的(de)(de)變(bian)化程度(du)(du)。