The Inhibition Mechanism Of The Oligomeric Surfactants Constructed By The Coordination Effect Of Rare Earth Metal Ions For The Aluminum Alloy Surface

Anticorrosion of the aluminum alloy in NaCl medium always is the important topicon industrial application and the fundamental research domain, and corrosion inhibitor isone of effective methods to exempt corrosion of the aluminum alloy in the NaCl medium.The aluminum alloy corrosion inhibitors with more effective includes: organic corrosioninhibitor and rare earth corrosion inhibitor, also both of them inhibite its corrosion ratethrough form protective film in the aluminum alloy surface. According to theunprecedented complex which forms by the surfactants and the rare earth ions,the researchobject of this paper is the corrosion inhibition performance on aluminum alloy surface inNaCl medium.To study the properties of C12H25N(CH2COONa)2(RNC-12) andC8H17N(CH2COONa)2(RNC-8), This paper used surface tension method. And thecorrosion inhibition performance of two surfactants, two rare earth ions(Ce3+、La3+), fourcomplexes on the2024#aluminum alloy in the3.5%NaCl medium was studied byweight-loss method, electrochemical impedance, electrochemical polarizationmeasurements and scanning electron microscopy (SEM).In the3.5%NaCl medium, the surfactants and the rare earth ions have the coordinatefunction to form the complex, and the complex has the very good inhibition performanceon the aluminum alloy surface corrosion. Through contrasting the corrosion inhibitionperformance of different kinds of corrosion inhibitors on the aluminum alloy, we obtain thecorrosion inhibition function rule. The results provide the experiment and the rationalechoose and determine the experiment condition for the best corrosion inhibitorperformance on2024#aluminum alloy. The main conclusions include:(1)Both RNC-12, RNC-8have the good surface activity, cmc value is1.10×10-3mol·L-1、2.40×10-3mol·L-1respectively. Both of them have the coordinatefunction to form the complex with Ce3+, La3+. The coordination number with rare earthions is2:3. (2)When Ce3+, La3+act as corrosion inhibitor, through forming Ce(OH)3, La(OH)3precipitation membrane in the aluminum alloy surface plays an inhibitory effect, itsconcentration of the best corrosion inhibitor performance is5×10-5mol·L-1,1×10-4mol·L-1respectively, the best corrosion inhibition efficiency reach80%.(3)When RNC-12, RNC-8act as corrosion inhibitor, form the adsorption membranethrough the adsorption on the aluminum alloy surface, its best concentration is1×10-4mol·L-1,5×10-5mol·L-1respectively, the best corrosion inhibition efficiency reach80%.(4)When RNC-12,RNC-8separately with Ce3+, La3+forms complexes act as thecorrosion inhibitor. The inhibition efficiency of them has enhanced because of theadsorption and the precipitation reaction, the corrosion inhibitor performance is better thansingle system. All of the best concentration are5×10-5mol·L-1, the best corrosion inhibitionefficiency reach or exceed95%.This paper has affirmed possibility that the surfactant constructed by the rare earthions to take as the corrosion inhibitor on aluminum alloy in NaCl medium. As the newcorrosion inhibitors, the corrosion inhibition theories of the surfactant and the rare earthions contacted.It not only retains the surfactant original characteristic, but also unfolds therare earth ions superiority. The research has the very high research value and theapplication prospect.