汽车轮毂用Mg-5.2Al-0.5Mn-1.8Ca合金板材的表面处理与耐腐蚀性能

Surface treatment and corrosion resistance of Mg-5.2Al-0.5Mn-1.8Ca alloy sheet for automobile hubs

在汽车轮毂用的Mg-5.2Al-0.5Mn-1.8Ca合金板材表面制备了3种不同防护层,对比分析了微弧氧化(MAO)、氟碳漆(FC)和聚酯漆(PP)防护层的表面形貌、截面形貌、与基体结合力、耐腐蚀性能和弯曲性能。结果表明,MAO、FC和PP防护层与镁合金基体的结合力分别为1.99、33.84和24.16 N,涂层厚度分别为10.68、67.06和55.35μm,且FC和PP防护层厚度符合QCT 484-1999标准中TQ2甲等要求;镁合金基体与表面防护层的耐腐蚀性能从低至高顺序为:镁合金基体与表面防护层的耐腐蚀性能从低至髙顺序为:镁合金基体<MAO<PP<FC,PP和FC防护层都具有优良的耐腐蚀性能;静态弯曲试验过程中FC防护层在弯曲位移达到15 mm附近时即发生表面破裂,而MAO和PP防护层在达到弯曲位移25 mm时也未见表面起皮或者破裂;动态弯曲试验过程中MAO、FC和PP防护层产生微裂纹时的反复弯折次数分别为3648、4269和5066次;PP防护层具有较好的耐腐蚀性能,且与镁合金基体的结合力较大、静态与动态弯曲性能较好,具有最佳的综合性能。

Three different protective coatings were prepared on the surface of Mg-5.2Al-0.5Mn-1.8Ca alloy sheet for automobile hubs.The surface morphology,cross-section morphology,adhesion with matrix,corrosion resistance and bending properties of the protective coating of MAO,FC and PP were compared and analyzed.The results show that the bonding strength of MAO,FC and PP protective coating to magnesium alloy matrix is 1.99,33.84 and 24.16 N,and the coating thickness is 10.68,67.06 and 55.35μm,respectively,and the thickness of FC and PP protective coating meets the requirements of TQ2 A in QCT 484-1999 standard.The order of corrosion resistance between magnesium alloy matrix and surface protective coating from low to high is magnesium alloy matrix,MAO,PP and FC,in which the PP and FC protective coating have excellent corrosion resistance.FC protective coating rupture on the surface when bending displacement reaches 15 mm during static bending test,while MAO and PP protective coatings do not peel or rupture on the surface when bending displacement reaches 25 mm.The repeated bending times of MAO,FC and PP protective coatings during dynamic bending test are 3648,4269 and 5066,respectively.PP protective coating has good corrosion resistance,strong bonding force with magnesium alloy matrix,good static and dynamic bending properties,and has the best comprehensive performance.