Study On Multi-Non-Phosphorus Scale And Corrosion Inhibitor

The use of heavy metal-based corrosion inhibitors is increasingly being curtailed by recentenvironmental restrictions. In many parts of the world, high content of phosphorus are alsorestricted by law. In response to these environmental guidelines, a new non-phosphorus andbiodegradable composite water treatment agent was synthesized in this paper.In order to solve the corrosion and scale problems at the same time, the optimal ratio wasdetermined by orthogonal tests. The performance of corrosion, scale inhibition andbiodegradability were investigated by rotary hanging-piece corrosion tests, electrochemical,scale inhibition tests and biodegradation experiments. The corrosion testing piece and scalesample were characterized by SEM. The inhibition property and inhibition mechanism areexplored.The best ratio of the components in the agent are as follow:itaconic acid homopolymer, 8mg·L-1polyepoxysuccinic acid(PESA), 8mg·L-1polyaspartic acid derivative(PASP-ASP), 20mg·L-1sodium gluconate, 100mg·L-1It has good performance of scale inhibition: Under the conditions of Ca2+ 645 mg·L-1, watertemperature 80℃, the scale inhibition rate of composite product was more than 96%; and it hasgood performance of corrosion: the corrosion rate was up to over 97%; it also has excellentbiodegradability: The efficiency of biodegradability reach to 43.26% in 7d and was up to over90% in 28d.Potentiostatic polarization curves revealed that: In the near neutral environment (pH = 6.0 ~9.0), The composite product has a strong ability to adapt the pH changing; When the theconcentration of Cl- was lower than 100mg·L-1, the composite product has a good resistance to chlorine; The temperature affected greatly on the efficiency inhibition, with the temperatureincreasing, the efficiency inhibition decreased: the efficiency inhibition was 55% when thetemperature was 55℃; The composite product also has good performance of by corrosion forcopper alloy.SEM micrograms of CaCO3 scale samples in the static experiments shows that: thecomposite product could split and distort scale crystals by disrupting their lattice structure andnormal growth patterns, which causing the calcium carbonate crystallite to get much finer andmore dispersive and hindering calcium carbonate crystallite to cling on the metal surface.The study of inhibition mechanism showed that: the composite water treatment agent whichwas an effective anodic type corrosion inhibitor can form a adsorption membrane on the metalsurface. The membrance will effectively improve the film resistance and charge transferresistance Rt and inhibite the corrosion reaction of the carbon steel. At the same time, thecomposite product can stabilize Fe3+ and other ions to disperse uniformly in water, which willavoide these ions to deposite on the metal surface and corrode under the scale.