The Synthesis And Mechanism Study On A Complex Phosphate-free Corrosion And Scale Inhibitor

This paper is based on the problems of corrosion and scaling that exist in opencirculating cooling water system, at the same time considering the pollution ofenvironment and water that caused by the commonly using of phosphorus watertreatment agent. A complex phosphate-free corrosion and scale inhibitor was preparedwith the main raw materials of acrylic-2-acrylamide-2-methylpropane sulfonic acidcopolymer (AA-AMPS), polyepoxysuccinic acid (PESA), zinc sulfate (ZnSO47H2O),sodium molybdate (Na2MoO42H2O) and sodium gluconate (NaGL).This research studied the calcium carbonate scale inhibition, the calciumphosphate scale inhibition and the ferric oxide dispersion performance of PESA andAA-AMPS respectively by calcium carbonate precipitation method, calcium phosphateprecipitation method and light transmittance method, and on the basis of this, a scaleinhibition and dispersion agent was obtained by the mixing experiments. The corrosioninhibition performance of it was tested by static weight-loss method. and EIS(electrochemical impedance spectroscopy) method as well. After that, select corrosioninhibitors to compound with the scale inhibition and dispersion agent by EIS method,and eventually get the compound corrosion and scale inhibitor. Then a study of thescale inhibition dispersion performance, the dynamic corrosion inhibition performanceto carbon steel, the corrosion inhibition performance to brass and the biodegradabilityof the compound agent was carried on. In the end, the corrosion inhibition and scaleinhibition mechanism were pilot studied by Tafel polarization-curve method and SEM(scanning electron microscope) method. The results are as follows: The best mass concentration of the components in thecompound corrosion and scale inhibitor is as follow:polyepoxysuccinic acid (PESA),10mg/Lacrylic-2-acrylamide-2-methylpropane sulfonic acid copolymer (AA-AMPS),10mg/Lzinc sulfate (ZnSO47H2O),6mg/Lsodium molybdate (Na2MoO42H2O),40mg/Lsodium gluconate (NaGL),100mg/LIt has excellent scale inhibition performance, the calcium carbonate scaleinhibition rate and the calcium phosphate scale inhibition rate can reach98.40%and99.80%respectively; It has good ferric oxide dispersion performance, the lighttransmittance is22.40%; It has superior performance of corrosion inhibition to carbonsteel, the corrosion inhibition rate is up to above92%,it has some corrosion inhibitionto brass too, the corrosion inhibition rate is32.02%; It also has well biodegradability,the efficiency of biodegradability reach to over85%in28d.SEM micrograms of calcium carbonate scale samples in the static experimentsshows that: joining the compound corrosion and scale inhibitor can inhibit thegrowth of the crystal lattice,distort lattice structure, thus to achieve the purpose of scaleinhibition.The study of the corrosion inhibition mechanism shows that: compound corrosionand scale inhibitor is an effective anodic type corrosion, which may form a protectivemembrane on the metal surface to achieve the aim of corrosion inhibition.