Scale And Corrosion Inhibitor With Low Molecular Organic Phosphonic Acid Is Developed

In recently years, the rapid development of industrial production brought about both the ever increasing demand for industrial cooling water and many problems such as corrosion and scale. Using corrosion and scale inhibitor is a convenient way with remarkable effect and less investment to solve these problems. In this paper, two kind of corrosion and scale inhibitors i.e. animo trimethylene phosphonic(ATMP) and1-hydroxyehyl-lidene-1,1-diphosphonic (HEDP) acid are synthesized, the research of corrosion and scale performance and the synergism of the two corrosion and scale inhibitors have been done.Firstly, ATMP was synthesized with formaldehyde, phosphorus tri-chloride and ammonium chloride. Optimized the synthetic process conditions by the comparison of each group of ATMP obtained through different synthetic conditions. Its structure was characterized by Infrared Spectrophotometer. The result indicated that the best synthetic process conditions were heat-preserving time for2.5hours at120℃, the mole ratio of phosphorus tri-chloride, formaldehyde, ammonium chloride was3:4:1.4, Infrared Spectrum indicated that the target product was obtained successfully. The effect of inhibitor’s concentration, temperature and corrosion time on the corrosion inhibition performance of ATMP was evaluated by weight-loss method, the result showed that with the inhibitor concentration of35mg/L and corroded for24hours at35℃, the corrosion rate was at minimum while inhibition efficiency at maximum. The effect of scale inhibitor’s concentration, temperature and pH on the scale inhibition performance was evaluated by resistance calcium-carbonate method. The result indicated that the scale inhibition efficiency was better with inhibitor’s concentration of lmg/L,ph=10,at the temperature of30℃.Secondly, HEDP was synthesized with phosphorus tri-chloride, acetic anhydride. Optimized the synthetic process conditions by the comparison of each group of HEDP obtained through different synthetic conditions. Its structure was characterized by Infrared Spectrophotometer. The result indicated that the best synthetic process conditions were reaction temperature at100℃, the mole ratio of (CH3CO)2O and PCl3isl:2, the drop speed of adding acetic anhydride was from fast to slow, Infrared Spectrum indicated that the target product was obtained successfully. The effect of inhibitor’s concentration, temperature and corrosion time on the corrosion inhibition performance of HEDP was evaluated by weight-loss method, the result showed that with the inhibitor concentration of10mg/L and corroded for24hours at60℃癈, the corrosion rate was at minimum while inhibition efficiency at maximum. The effect of scale inhibitor’s concentration, temperature and pH on the scale inhibition performance was evaluated by resistance calcium-carbonate method. The result indicated that the scale inhibition efficiency was better with inhibitor’s concentration of lOmg/L, ph=9, at the temperature of60℃.Thirdly, the synergism of the two corrosion and scale inhibitors have been done and the result indicated that The inhibition rate is95.61%when the mole ratio between ATMP and HEDP was3:2,the inhibition rate increased by13.70%while compared with HEDP alone. The inhibition rate is92.03%When the concentration of [Ca2+]=250mg/L in the stimulate circulation cooling water. Maximum inhibition rate reached93.46%when the mole ratio between ATMP and HEDP was2:3. The inhibition rate increased by1.74%while compared with HEDP alone.the scale inhibition efficiency kept more than90%when the concentration of Ca2+was between50mg/L and150mg/L.Finally, study on the corrosion and scale inhibition mechanism of the two inhibitors was tested by electrochemical methods and scanning electron microscopy. The electrochemical polarization curves indicated that ATMP was an anode-based mixed-type corrosion inhibitor while HEDP was a cathode-based mixed-type corrosion inhibitor, and the synergy of the two inhibitors was also a mixed-type corrosion inhibitor. The SEM observations showed that the corrosion of K55steel was inhibited after adding corrosion inhibitors and the corrosion product film was more homogenous than that without the existence of corrosion inhibitors. The corrosion extent was less and the corrosion inhibition efficiency after adding the compounded inhibitors, and the corrosion product film was more homogenous and compact thus prevented the sample from contacting with the corrosion medium and protected the steel much better.Inhibition mechanism:ATMP can form a stable complex with Ca2+, Mg2+and other ions in water. It can play an interference effect to the scale layer growth of CaCO3that has been formed. Undermine the growth of CaCO3and achieve the scale effect. HEDP molecule contains two phosphorylation foundation group that with a negative charge. Negatively charged oxygen ions are prone to strong electrostatic interaction with calcium that is on the surface of CaCO3and achieve the scale effect.