微弧氧化镁合金表面化学镀镍层的生长行为与耐蚀性.docx

微弧氧化镁合金表面化学镀镍层的生长行为与耐蚀性
摘要：
本文研究了微弧氧化(MAO)镁合金表面化学镀镍层的生长行为和耐蚀性。采用扫描电子显微镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)、电化学腐蚀测试和印迹测试等多种方法对样品进行了表征和测试。结果表明，MAO处理后的镁合金表面形成了均匀致密的氧化层，并在氧化层上形成了化学镀镍层。化学镀镍层的生长与前驱体电极化和镍离子扩散控制有关，反应速率随着前驱体电极化电位的提高而增加。表面镍含量的变化与草酸钠浓度的变化有关，在草酸钠浓度为0.2mol/L时得到表面镍含量最高的化学镀镍层。化学镀镍层的存在显著提高了镁合金的耐蚀性。
关键词：微弧氧化；镁合金；化学镀镍；生长行为；耐蚀性
Introduction：
Magnesium(Mg)alloyhasattractedincreasingattentionduetoitsexcellentpropertiessuchaslowdensity,highspecificstrength,goodmachinability,andgooddampingcapacity.However,itspoorcorrosionresistancelimitsthepracticalapplicationofMgalloy.InordertoimprovethecorrosionresistanceofMgalloy,varioussurfacemodificationmethodshavebeendeveloped.Amongthem,micro-arcoxidation(MAO)hasbeenwidelyusedduetoitsabilitytoformadenseanduniformceramiccoatingonthesurfaceofMgalloy.However,theMAOcoatingisstillpronetocorrosioninsomecorrosiveenvironments.Therefore,inthisstudy,achemicalnickelplatinglayerwasdepositedonthesurfaceofMAO-treatedMgalloytofurtherimproveitscorrosionresistance.
ExperimentalProcedure：
TheMgalloyusedinthisstudywasAZ31B,whichwascutinto20mm×20mm×2mmpiecesandpolishedwithabrasivepaperofdifferentsizes.MAOtreatmentwascarriedoutusingaMAOpowersupply.TheelectrolyteusedintheMAOprocesswasasolutioncontaining1g/Lsodiumsilicate,0.5g/LNa2WO4·2H2O,and0.2g/LNaF.TheMAOprocesswascarriedoutundertheconditionsofaconstantvoltageof400Vandapulsefrequencyof500Hzfor10min.AfterMAOtreatment,thesampleswerecleanedwithdistilledwateranddried.ThechemicalnickelplatinglayerwasdepositedonthesurfaceoftheMAO-treatedMgalloyusinganickelplatingsolutioncontaining0.05Mnickelsulfatehexahydrate,0.3Msodiumcitratetribasicdihydrate,and0.2MNaOH.Thedepositionprocesswascarriedoutatdifferentappliedpotentialsfordifferentperiodsoftime.
ResultsandDiscussion：
TheSEMimagesoftheMAO-treatedMgalloysurfacebeforeandafternickelplatingareshowninFigure1.ItcanbeseenthattheMAO-treatedMgalloysurfaceiscoveredwithauniformanddenseoxidelayer.Afterchemicalnickelplating,auniformandcompactnickellayerwasdepositedonthesurfaceoftheMA