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)霧(wu)(wu)(wu)(wu)測試(shi)(shi)(shi)(shi)(shi)(shi)主要包括四(si)種方法，中(zhong)性(xing)(xing)(xing)鹽(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)、銅鹽(yan)(yan)(yan)(yan)(yan)(yan)加速醋酸鹽(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)、醋酸鹽(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)和交(jiao)變鹽(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)。 中(zhong)性(xing)(xing)(xing)鹽(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)，又稱NSS試(shi)(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)，是(shi)(shi)(shi)目前(qian)應用(yong)領域最(zui)廣(guang)、出(chu)現最(zui)早的(de)(de)(de)一種加速腐(fu)蝕(shi)試(shi)(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)方法。一般采用(yong)5%的(de)(de)(de)氯化(hua)鈉(na)鹽(yan)(yan)(yan)(yan)(yan)(yan)水溶(rong)(rong)液(ye)，將(jiang)溶(rong)(rong)液(ye)PH值(zhi)調在(zai)中(zhong)性(xing)(xing)(xing)范圍(6.5～7.2)，作為(wei)噴(pen)霧(wu)(wu)(wu)(wu)使用(yong)。試(shi)(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)溫度(du)(du)控制在(zai)35℃，鹽(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)的(de)(de)(de)沉(chen)降(jiang)率(lv)應為(wei)1～2ml/80cm/h。 銅鹽(yan)(yan)(yan)(yan)(yan)(yan)加速醋酸鹽(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)，又稱CASS試(shi)(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)，是(shi)(shi)(shi)近幾年(nian)發(fa)(fa)展起來(lai)的(de)(de)(de)一種快速鹽(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)腐(fu)蝕(shi)試(shi)(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)。試(shi)(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)溫度(du)(du)為(wei)50℃，鹽(yan)(yan)(yan)(yan)(yan)(yan)溶(rong)(rong)液(ye)中(zhong)加入少(shao)量銅鹽(yan)(yan)(yan)(yan)(yan)(yan)-氯化(hua)銅，具有(you)強(qiang)烈誘發(fa)(fa)腐(fu)蝕(shi)能(neng)力(li)，腐(fu)蝕(shi)速度(du)(du)是(shi)(shi)(shi)NSS試(shi)(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)的(de)(de)(de)8倍左右(you)。 醋酸鹽(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)，又稱ASS試(shi)(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)，是(shi)(shi)(shi)建(jian)立在(zai)中(zhong)性(xing)(xing)(xing)鹽(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)的(de)(de)(de)基礎(chu)上(shang)發(fa)(fa)展而來(lai)的(de)(de)(de)。在(zai)5%氯化(hua)鈉(na)溶(rong)(rong)液(ye)中(zhong)加入冰醋酸，將(jiang)溶(rong)(rong)液(ye)的(de)(de)(de)PH值(zhi)降(jiang)為(wei)3左右(you)，溶(rong)(rong)液(ye)變成酸性(xing)(xing)(xing)，最(zui)后形成的(de)(de)(de)鹽(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)也由中(zhong)性(xing)(xing)(xing)鹽(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)變成酸性(xing)(xing)(xing)。其腐(fu)蝕(shi)速度(du)(du)是(shi)(shi)(shi)NSS試(shi)(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)的(de)(de)(de)3倍左右(you)。 交(jiao)變鹽(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)則是(shi)(shi)(shi)屬于(yu)綜(zong)合鹽(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)，它(ta)的(de)(de)(de)原(yuan)理是(shi)(shi)(shi)在(zai)中(zhong)性(xing)(xing)(xing)鹽(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)的(de)(de)(de)基礎(chu)上(shang)加恒定濕(shi)熱的(de)(de)(de)試(shi)(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)。主要用(yong)于(yu)空腔型的(de)(de)(de)整機(ji)產(chan)(chan)品(pin)(pin)(pin)，通過(guo)潮濕(shi)環境(jing)的(de)(de)(de)滲透(tou)，使鹽(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)腐(fu)蝕(shi)既在(zai)產(chan)(chan)品(pin)(pin)(pin)表面發(fa)(fa)生(sheng)(sheng)，也在(zai)產(chan)(chan)品(pin)(pin)(pin)內(nei)部(bu)發(fa)(fa)生(sheng)(sheng)。交(jiao)變鹽(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)試(shi)(shi)(shi)(shi)(shi)(shi)驗(yan)(yan)將(jiang)產(chan)(chan)品(pin)(pin)(pin)環境(jing)在(zai)鹽(yan)(yan)(yan)(yan)(yan)(yan)霧(wu)(wu)(wu)(wu)和濕(shi)熱兩種條件下不(bu)斷替換，最(zui)后評估整機(ji)產(chan)(chan)品(pin)(pin)(pin)的(de)(de)(de)電性(xing)(xing)(xing)能(neng)和機(ji)械性(xing)(xing)(xing)能(neng)的(de)(de)(de)變化(hua)程度(du)(du)。