無鉻前處理對預塗散熱鋁片表面特性影響之探討

Effects of Chrome-Free Treatment to the Pre-Coated Aluminum Film Properties

無鉻型金屬表面處理是環保趨勢，也是先進國家產品環保法規的要求。歐盟率先以WEEE及RoHS等法令來限制特定有毒物質使用及其廢棄物的污染。以往鋁片的表面處理產品都經過含鉻酸藥劑處理，以增進鋁片在後續上漆的附著性及耐蝕性。目前世界各大廠家都嘗試採用環保無鉻處理的作法，取代含鉻處理劑，以符合環保產品標準；並可以避免人員環境污染及後續含鉻廢水處理問題。本研究以引進國內外的無鉻處理劑，配合產製製程，藉由實驗室的評估篩選出合格的處理劑，並進一步塗製塗膜鋁散熱片。以實驗計劃法，探討各種無鉻處理劑之影響因素，分析對後續預塗散熱片親水性及耐蝕性的影響。進行處理劑種類濃度、反應溫度、時間及處理後塗漆前放置時間等品質重要影響因素的評估測試。研究結果顯示，產製之預塗鋁散熱片，可通過750小時鹽霧耐蝕性試驗，RN值≥9.3，實用親水性接觸角≤50°，其餘塗膜品質皆達標準。另，經由直交實驗及S/N比分析顯示，塗膜親水性受處理劑種類濃度、反應時間影響較大；預塗鋁散熱片之耐蝕性受處理劑種類濃度影響較為明顯。

Chrome-free surface treatment of metal is the trend of environment protection, and also the regulations for the related products. Recently, there are WEEE and RoHS directions in EU for restriction of toxic substances and its waste. Since chromium is good surface treatment agents for its good adhesion and corrosion prevention in the surface of aluminum. Chromium content chemicals have been used for a long time in the coated aluminum sheet. Several chrome-free chemicals were submitted by different chemical suppliers. Refer to the manufacturing process and chemicals are evaluated to make the coated high hydrophilic and corrosion resistance for precoated fin-stock aluminum sheet. This study evaluates the chrome-free process and chemicals to develops suitable chemicals for the hydrophilic and high corrosion resistance products. The quality of pre-coated fin stocks will meet the criterion of cyclic test, hydrophilic contact angles ≤ 50 ° and corrosion resistance value (SST 750 hrs) RN ≥ 9.3. The approach of experiments included experimental planning methods to investigate the effects of concentration of chemicals, treatment periods, baking temperature and the interval between treatment and painting. As a result, the selected chrome-free chemical could produce the high hydrophilic and corrosion resistance qualities and reached the characters of the product. The results of orthogonal experiment and the analysis of signal-to-noise (S/N) ratio also shows corrosion resistance and hydrophilic contact angles significantly affected by concentration of chemicals, treatment periods, and the value of hydrophilic contact angles significantly affected by the brand of chemical, film build thickness also. This study could be used to assist the chrome-free process and adjust the qualities of the precoated fin-stock for its performance.