Synthesis and inhibition behavior of acid stimuli-responsive Ca-Na2MoO4-HNTs nanocomposite

Halloysite nanotubes (HNTs) are the natural clay mineral with a tubular structure, which can be used as the nanocontainer for loading corrosion inhibitor. In this work, Na2MoO4 was loaded into HNTs (defined as "Na2MoO4-HNTs") through vacuum negative pressure method. In order to control the release rate of Na2MoO4 from Na2MoO4-HNTs, the insoluble CaMoO4 complex was introduced at the end of tubes through the interaction between Na2MoO4 and Ca2+ to obtain Ca-Na2MoO4-HNTs. The surface morphology was investigated by transmission electron microscope (TEM), and the release behavior was determined by UV-vis spectrophotometer. The inhibition behavior of CaNa2MoO4-HNTs for Q235 steel in 3.5% NaCl solution was investigated by electrochemical impedance spectrum techniques. The results show that Ca-Na2MoO4-HNTs owns insoluble CaMoO4 complex capping the end of HNTs, and the total loading capacity of Na2MoO4 is about 14.6%. Moreover, the tunable release of Na2MoO4 can be achieved by controlling the strength of the CaMoO4 complex stoppers at the end of HNTs, and the release time of Na2MoO4 can be prolonged to more than 600 min. Importantly, the release rate of Na2MoO4 will increase sharply in acid solution, owing to the decomposition of CaMoO 4 complex. In addition, Q235 steel in 3.5% NaCl solution + 1.0 g/L Ca-Na2MoO4-HNTs exhibits higher inhibition efficiency (60.62% at 24 h) than Q235 steel in 3.5% NaCl solution.