钢铁表面锆盐-植酸复合转化膜的制备及性能

Preparation and Performance of Zirconium Salt/Phytic Acid Composite Conversion Coaling on Steel Surface

目前，将植酸与锆盐复合转化膜用于钢铁表面防护的研究较少。采用氟锆酸钾和植酸在A3钢表面制备了具有良好耐蚀性能的灰色锆盐-植酸复合转化膜，确定了转化液的组成及成膜工艺条件。采用扫描电镜（SEM）、能谱分析（EDS）、傅里叶变换红外光谱（FTIR）、电化学测试及中性盐雾试验（NSS）对复合膜的形貌、成分、成膜过程电位特性及耐蚀性进行分析。结果表明：锆盐-植酸复合转化最优工艺为10g/L氟锆酸钾，1．0mL／L植酸，pH值3．8—4．0，反应温度60℃，反应时间1．5h；钢铁经最优工艺处理所得复合膜的自腐蚀电位比未加植酸所得锆盐膜的正移了48mv，自腐蚀电流密度下降约10％，低频区电化学阻抗值提高了近2倍，耐中性盐雾时间增加24．0h．钢铁的耐腐蚀性能显著提高。

A gray zirconium salt / phytic acid composite conversion coating with excellent corrosion resistance was prepared on A3 steel by using potassium fluozirconate and phytic acid,and the composition of conversion solution and technological conditions were optimized.The scanning electron microscope(SEM),energy spectroscopy(EDS),Fourier transform infrared spectroscopy(FUR),electrochemical tests and salt spray test(SST) were used to study the morphology,composition,potential characteristic during forming process and corrosion resistance of coating.Results showed that the optimized conditions were as follows:10 g/L potassium fluozirconate,1.0 ml/L phytic acid,pH=3.8~4.0,reaction temperature of 60℃ and reaction time of 1.5 h.After treated under the optimized conditions,the composite coating formed on steel possessed free corrosion potential,more positive 48 mV than zirconium salt coating.Moreover,the corrosion current density of composite conversion coating reduced by about 10%,and the impedance at the low-frequency region increased by 2 times,as well as the salt spray time increased by 24 h.Therefore,the corrosion resistance of steel was improved greatly.