| Making use of corrosion inhibitors in reason is an efficient method to prevent the metal and its alloy from eroding in environmental medium. Corrosion inhibitor technique with favorable effect and high economic benefit had been one of the most abroad anticorrosive techniques applied nowadays such industry as producing and processing petrochemicals, chemical rinse, atmosphere environment, water usage in industry, instrument and meter manufacturing etc. With the advent of oceanic century, corrosion inhibitors have an important function during the course of developing and utilizing seawater. But some poisonous and deleterious inhibitors have been confined of forbidden in use. Research and development of green corrosion inhibitors had been necessitous. According as research and development of green corrosion inhibitors, WTdeveloped three-compound inhibitor. The addition ratio was obtained by Latin experiment. Its critical concentration studied by weight loss trials was 350mg/L and inhibitory efficiency was 92.8% at this concentration. In order to prevent local corrsoion NaaSiOs and NaaWCU were added to form a five-compound corrosion inhibitor. The best weight ratio of Calcium gluconate, Zinc sulfate, APG, Na2SiO3 and Na2WO4 was studied by Latin experiment too. Its critical concentration also studied by weight loss trials was 280mg/L and inhibitory efficiency was 93.8% ?t this concentration. The inhibitor can inhibit local corrosion well at the critical concentration. In this way, a kind of high effect corrosion inhibitor was obtained.Inhibitory capability was tested by weight loss and electrochemistry trials in order to examine its inhibitory effect in different conditions.The results of experiment that filmed on mild steel beforehand at high inhibitor concentration revealed the inhibitor was type of film-formed inhibitor. Its criticalcone: itration dropped to 21 Omg/L after filmed beforehand.The inhibitory effect for mild steel rusted in advance and intermittent marinating was studied by weight loss trials. And inhibitory capability in different medium was tested by weight loss and electrochemistry trials. When the concentration reached 280mg/L, its inhibitory efficiency was 91.6% for intermittent marinating mild steel. But the inhibitory efficiency was less than 80% for rusted mild steel at the concentration of 350mg/L.This inhibitor has good inhibitory effect for mild steel from 18 to 50 in seawater and salinity or low velocity of seawater has no effect on inhibitor's function. When the temperature exceeded 60 the inhibitor's effect was not fine.The inhibitor's aftereffect was studied by subsection experiment and EIS. The results of subsection experiment showed that inhibitory efficiency keep 92% upwards at all times within 1080h. The causticity of the medium enhanced and the velocity of mild steel in this medium weakened. The results of EIS indicated inhibitory film Lad formed primarily after 24h. The film's function swelled gradually along with prolonging experimental time and the film had good effect within 545h.By comparing with other inhibitors we known the inhibitor mentioned above had best inhibitory capability.Inhibitory mechanism was studied by electrochemistry methods such as polarization curve, EIS, CV etc and SEM.(1) Results of polarization curve showed that the inhibitor was mix-type inhibitor, which mainly inhibited anodic process. (2) The reaction of forming film had three stages: fistly, corrosion inhibitor adsorbed on mild steel surface primarily; secondly, the fH inhibitor's film formed after 48h; finally, multiplayer film formed. (3) The film formed in lOOOmg/L inhibitor solution within 48h had short life in blank seawater, shorter than 48h; But this film had long life in the system of 21 Omg/L inhibitor + seawater, this film had gone intact and firm and had good effect for mild steel within 552h. These results were consistent with weight loss experiments'. (4) Mild steel's nil-charge potential was -0.6V(vs SCE) in seawater. Inhibitor had strong adsorptive function from -0.5V to... |
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