The Alternating Currents Corrosion Conduction Research On The Materials Of Underground Pipelines

This thesis begins with testing whether or not existing alternation stray current around the electric pump well, by means of analyze the results of the two alternating current corrosion experiments (they are constant temperature waters stray alternating current corrosion experiment indoors and corrosion experiment on metal specimens buried in underground which are endured alternating current), research on the alternating currents corrosion conduction to the materials of underground pipelines as the following aspects: (1) the effect of alternating current voltage on corrosion rates; (2) the effect of resistivity on corrosion rates; (3) the effect of temperature on corrosion rates; (4)the relationship between average AC current density and weight loss; (5)the relationship between average AC current density and time; (6)according to the relationship between expose area and weight loss, the electric field intensity theory is advanced; with the aid of the modern analyze and examine technique and method, the corrosion morphology character about corroded steel specimens' surface were observed by scanning electron microscope and energy spectrum analysis are output, the chemical analysis of the constant temperature waters corrosive product is done and the form process of corrosive product is discussed. From the experiment result of metal specimens buried in underground, discussing the influence of AC stray current on cathode protection by using galvanic anode method.Research results indicate: (1) under low temperature and low resistivity ,with AV raising specimens' corrosion rates trend to accretion;while under high temperature and high resistivity , with AV raising specimens' corrosion rates trend to minish; (2) the effect of resistivity on corrosion rates indicate: under low temperature and low resistivity, resistivities are higher, corrosion rates are lower; the main reason is : compared with higher resistance ratio solution with lower resistance ratio has larger ion consistency. Specimen with the same expose area, when ion consistencies are larger , they have more probability to contact specimen,and have more probability to react,then "resistivities are lower,corrosion rates are higher" appears. (3) under this experiment condition.temperature is not the main reasion to corrosion ratio; ( 4 ) the influence of average AC current density is very prominence,with AC current density raising specimens' corrosion rates trend to accretion; the main reason about alternating current corrosion on pipeline material is Mow current flows small area,then produce high current density; (5) the relationship between expose area and weight loss indicates:with expose area accretion, specimens' corrosion rates trend to minish. experiment results indicate:alternating current corrosion have relation with voltage Resistance ratio,average current density and expose area . and protective performance about galvanic anode decline when stray current exists.Finally according to the experiments results and literatures and materials, three alternating current theorys was summaried and put forward:electrochemistry theory,electric field intensity theory and electric attack hypothesis. And suggest using diode and galvanic anode method to alleviating AC stray current corrosion.