(1. 新冶高科技集團有限公司先進金屬材料涂鍍國家工程實驗室, 北京 100081；
2. 國家知識產(chǎn)權(quán)局專利局專利審查協(xié)作廣東中心，廣州 510530)
摘 要: 采用SEM觀察了成分不同熱鍍鋅合金鍍層的微觀結(jié)構(gòu)和鍍層腐蝕后的表面形貌，用電化學和循環(huán)腐蝕試驗分析鍍層鋼板的腐蝕行為和耐蝕性能，并用XRD分析鍍層表面腐蝕產(chǎn)物的相組成。結(jié)果表明：熱鍍鋅鋁鎂鍍層中Al、Mg及Zn2Mg相的存在可以使鍍層表面形成穩(wěn)定的化合物，降低電化學試驗時鍍層的電流密度和溶解速度；鍍層中的共晶相可以使Mg元素在鍍層中均勻分布，從而抑制陰極反應(yīng)；鍍層腐蝕后形成的Zn5(OH)8Cl2·H2O和Zn6Al2(OH)16CO3·4H2O是不溶性的膠狀腐蝕產(chǎn)物，可以有效隔斷鍍層與外界物質(zhì)間的電子傳輸。腐蝕初期，Zn2Mg優(yōu)先溶解，為腐蝕產(chǎn)物提供足夠的Mg元素，部分Mg元素進入Zn的腐蝕產(chǎn)物中，形成Zn5(OH)8Cl2·H2O和Zn4CO3(OH)6·H2O。而Al3+和Mg2+的存在可以降低鍍層中Zn4CO3(OH)6·H2O脫水形成無保護作用ZnO的趨勢，增加Zn5(OH)8Cl2·H2O和Zn6Al2(OH)16CO3·4H2O等腐蝕產(chǎn)物的量，且Zn5(OH)8Cl2·H2O和Zn4CO3(OH)6·H2O填充于腐蝕縫隙中可以進一步阻止腐蝕的發(fā)生，使得鍍層表面獲得更低的電位，因而對陽極的分層擴散驅(qū)動力變小，降低切邊部位在長期腐蝕中的溶解情況，提高鍍層的耐蝕性能和切邊保護性能。
關(guān)鍵字: 熱鍍鋅鋁鎂鍍層；顯微組織；電化學；循環(huán)腐蝕試驗；切邊保護性能；耐腐蝕機理
（1. National Engineering Laboratory of Advanced Coating Technology for Metals,
New Metallurgy Hi-Tech Group Co., Ltd., Beijing 100081, China;
2. Patent Examination Cooperation Center, Patent Office, SIPO, Guangdong, Guangzhou 510530, China）
Abstract:The microstructure and surface morphology after corrosion of the hot-dip galvanizing alloy coating with different components were observed by scanning electron microscopy, the corrosion performance and corrosion resistance of coating were analyzed by the electrochemistry and cyclic corrosion test, and the phase composition of corrosion product on the coating surface was analyzed by X-ray diffractometry. The results show that the corrosion current density of galvanized Zn-Al-Mg alloy coating is lower than that of zinc coated steel in electrochemical test, which proves that the existing of aluminum, magnesium and Zn2Mg phase can make the stable compounds form on the surface of coating and reduce the dissolution rate of zinc. The eutectic phase can make the Mg element uniformly distribute in the galvanized Zn-Al-Mg alloy coating, and inhibit the cathode reaction. Zn5(OH)8Cl2·H2O and Zn6Al2(OH)16CO3·4H2O are insoluble colloidal corrosion products of galvanized Zn-Al-Mg alloy coating after corroded, which can cut off the electronic transmission between coating and external substance, effectively. Zn2Mg is dissolved preferentially in the initialcorrosion,whichprovidesenoughMgelementsforthecorrosionproducts,part of Mg elements dissolve from thesurface of coating, get into the corrosion products of zinc, and form Zn5(OH)8Cl2·H2O and Zn4CO3(OH)6·H2O. However, the exist of Al3+ and Mg2+ can reduce the trend that Zn4CO3(OH)6·H2O dehydrated to from zinc oxide without protective effect, and increase the amount of Zn5(OH)8Cl2·H2O and Zn6Al2(OH)16CO3·4H2O in galvanized Zn-Al-Mg alloy coating. And the chemical compound of Zn5(OH)8Cl2·H2O and Zn4CO3(OH)6·H2O can be full in the corrosion cracks that furthermore prevent corrosion occurring in the coating, so, the lower potential is obtained on surface of coating, thus, the hierarchical diffusion driving force of anode becomes small, which can reduce the dissolution of cut-edge part of galvanized Zn-Al-Mg alloy coating in the long-term corrosion and improve the corrosion resistance and cut-edge protection performance of galvanized Zn-Al-Mg alloy coating.
Key words: hot dip galvanized Zn-Al-Mg alloy coating; microstructure; electrochemistry; cyclic corrosion test; cut-edge protection performance; corrosion resistance mechanism
