摘要
研究了AZ31B镁合金在羟基乙叉二膦酸(HEDP)溶液中的转化行为,并初步探讨了双膦酸化学转化体系的沉淀吸附防护机理。运用动电位极化扫描和极化阻抗法,比较分析了不同pH和HEDP浓度时转化膜的耐蚀性。结果表明,pH是关键影响因素。pH=1值时转化膜的耐蚀性最佳,腐蚀电位正移0.25 V,腐蚀电流密度降低近2个数量级(从57.3μA/cm2降至0.8μA/cm2),明显提高了镁合金的耐蚀性能。通过扫描电镜(SEM)分析表观形貌得知,膜层呈干涸河床状网络裂纹结构,且随pH升高,裂纹的宽度与深度增大,不利于膜层的抗腐蚀。
The conversion behavior of AZ31B magnesium alloy in hydroxyethylidene diphosphonic acid （HEDP） solution was studied. The precipitation-adsorption mechanism of HEDP conversion coating was briefly discussed. The corrosion resistance of the conversion coatings obtained at different pH values and HEDP concentrations was compared by potentiodynamic polarization sweep method and polarization resistance measurement. The results indicated that pH value is a key influencing factor. The conversion coating obtained at pH 1 has the best corrosion resistance due to the fact that its free corrosion potential shifts 0.25 V positively, and its corrosion current density reduces approximately by two orders of magnitude from 57.3 μA/cm2 to 0.8μA/cm2, remarkably improving the corrosion resistance of AZ31B alloy. The coating morphologies observed by scanning electron microscope （SEM） displayed a network structure with micro-cracks （like dry riverbed）, and the width and depth of cracks are increased with the increasing of pH value of treat solution, which is disadvantageous against corrosion resistance for conversion coating.
出处
《电镀与涂饰》
CAS
CSCD
北大核心
2013年第10期33-36,共4页
Electroplating & Finishing
基金
新加坡教育部创新基金(MOE2010-IF-1-027)
关键词
镁合金
二膦酸
转化膜
耐蚀性
电化学
形貌
magnesium alloy
diphosphonic acid
conversion coating
corrosion resistance
electrochemistry
morphology
