A Cellular Automata Simulation Of The Reclaimed Water Pipe Corrosion

Reclaimed water corrosion is a process involving microscopic,mesoscopic and macroscopic reactions.Among them,Processes including electrochemical reaction of corrosion and the growth of corroded products can be classified as mesoscopic scale.This thesis,using a typical simulating approach,cellular automata,divided the metal-corrosion system as discrete and ordered cellular space.Simple evolution rules were used to reconstruct corrosion process,while probability coefficients of reactions were introduced to simulate the randomness.Coupled with corroded morphology evolution graphs and statistical indicators,reclaimed water corrosion was analyzed under mesoscopic scale,which brought up a new idea to establish corrosion mechanism model using cellular automata(CA,for short).The thesis is composed by four parts.Firstly,made research about reclaimed water corrosion mechanism,present a physical model in accordance with CA idea.Then,a corresponding CA model was brought up based on CA definition.After then,design the details of CA model,among which evolution rules are the essence of the model.Matlab programming language was used to express and analyze the model.Vary the condition and coefficients of the model,as well as analyze the different corroded morphology,corrosion rate and other indicators,in order to investigate the corrosion kinetics.Lastly,make contrast with the simulated and experiment outcomes,try to conclude a reasonable description of corrosion mechanism.The results can be concluded as follows:(1)The corroded morphology evolution graphs can reproduce the corrosion process intuitively.As the anode reaction probability coefficient(rc)and iteration steps increased,corrosion became more and more serious.For evenly corrosion,there appeared more dramatic and irregular fluctuations on the metal surface,the size of corroded pits increased gradually while the corroded products increasingly accumulated.For local pitting,the corroded pits expanded its size downwards and to both sides.(2)When rc fixed,the range of corroded depth rose up as the time increased.When the shape of the corrosion depths curve along the horizontal direction were close and neat,along with a smaller varying range,the corrosion rate and the roughness of corroded surface was low,which shows that corrosion degree can be slight.Otherwise,roughness was high and corrosion degree can be serious.(3)Initially,the general corrosion rate was at the high level,then fluctuating downward until to a lower level and maintained a stable balance.It can be described as three stages: higher corrosion rate as rapid-corrosion stage,decreased corrosion rate as slow-corrosion stage and stable corrosion rate as stable-corrosion stage.The cumulative corrosion proportion of local pitting augment greatly exponentially,while general corrosion rate increased linearly,which showed that local pitting can lead to serious corrosion.(4)When the concentration of chloride ions and probability of hydrolysis acidification increased,the corrosion rate increased.The promotion effect would be more and more evident as the coefficients increased.(5)Make a comparison of outcomes from simulation and drinking water,reclaimed water experiments,it can be reached that the curve of cumulative corrosion proportion and general corrosion rate under evenly corrosion condition between were consistent.Especially the corrosion rate one can be divided into the three stages as rapid,slow and stable ones.