Research Of The Corrosion Law Of The Effect Of Chloride Ions On The Water Supply Pipelines In The Soil

Saline soil is widely distributed in China.Water supply pipelines buried underground suffered soil corrosion,which affecte the safety of water supply seriously.Sothe Research of the corrosion law of the effect of chloride ions on the water supply pipelines in the soil has great significance.In this paper,indoor accelerated buried test and electrochemical method are used to study the corrosion law of ductile iron pipelines?gray cast iron pipelines?A3 carbon steel pipelines.The main research contents are as follows:(1)Indoor accelerated buried test was used.Ductile iron pipelines?gray cast iron pipelines?A3 carbon steel pipelines were buried in the soil for 1 week?3weeks?5weeks?7weeks?10weeks.After these period of time,metal specimen was taken out to take pictures?SEM test?XRD test?measure the weight loss and other experiment treatment.Corrosion morphology?products?rate were studied in the soil which the mass percent of chloride ions are 0.015%?0.065%?0.115%?0.315%?0.515%?1.015%.(2)Electrochemical method are used.Ductile iron pipelines?gray cast iron pipelines?A3 carbon steel pipelines were made as the working electrode which working area are 1 cm2.Potentiondynamic and EIS test were taken to study the instantaneous corrosion rate and corrosion layer structure.The main conclusion are as follows:(1)With the mass percent of chloride ion increase,the corrosion rate of ductile iron pipelines?gray cast iron pipelines?A3 carbon steel pipelines increase,and the corrosion form developed from uniform corrosion to localized corrosion.(2)The SEM results showed that the corrosion products of the three kind of water supply pipelines had regular crystal shape and were flake.The XRD results showed that there was a critical mass percent of chloride ions,when the mass percent of chloride ions was above this percent,the?form corrosion products showed up.The critical mass percent of chloride ions of gray cast iron pipelines is 0.115%.ductile iron pipelines and A3 carbon steel pipelines were 0.065%.(3)As corrosion progressed,the corrosion rate decreased and tended to a constan value finally.The corrosion resistance of ductile iron pipelines were better than gray cast iron pipelines and the corrosion resistance of A3 carbon steel pipelines were worst.(4)The EIS results showed that ductile iron pipelines?gray cast iron pipelines?A3 carbon steel pipelines showed a capacitive arc two time constants and were controlled by diffusion cathode.Metal surface corrosion layer mainly for electric double layer capacitor.