| Prevention and cleanup of marine fouling organisms has been a problem for ships, marineengineering and biology works. Fouling of sea creatures would reduce ship speed and increasesurface friction, fuel consumption and drydocking maintenance times; When biofouling occurredat ships seawater systems and valves, it caused the flow rate decreases, or even blocked. Now,paint was a method which commonly used to prevent fouling of sea creatures. However, there area lot of anti-fouling paint defects, such as anti-fouling effect is not long term, the film strength isnot ideal. In addition, at seabed doors and other special parts, organic antifouling coatings couldbe easily peeled off due to the high water flow rate, so the current commonly used antifoulingcoating could not achieve antifouling effect.For fouling of marine organisms on the ship and marine engineering structures, combining aseries of advantages of cold spray coating, cold spray Cu-Cu2O coating for antifouling wasprepared. In the paper, microstructure, electrochemical characteristics and antifouling effect of thecoating were studied, and the copper leakage rate prediction system based on BP artificial neuralnetwork was established.At temperature of400℃, pressure of2.5MPa and spraying distance of40mm, using Cu andCu2O powder as raw material, the Cu-Cu2O coating prepared by cold spray technology had highdensity and excellent uniform. In the spraying process, Cu2O disproportionation reaction did notoccur massively and Cu2O deposited in the coating intact; Cu particles plastically deformed,combined together closely to form a coating in the way of mechanical interlocking andmetallurgical bonding. Coating of various components each had a low porosity, so it caneffectively prevent the infiltration of seawater and other corrosive media, exhibiting goodcorrosion resistance. The porosity of the coating increases with the decrease of the Cu2O content.Deformation of the particles in the coating was sufficiently and it had good density. Flat rate of the copper particles and hardness of the coating increased with increasing the content of Cu2O.Deformation of particles and hardness of the coating exhibited a causal relationship.The formation ofCu Cladsby adsorpting Cl-on the coating surface started the wholereaction. Then reacted in two competitive progresses which were active anodicdissolution and formation of the oxide film. The corrosion of the coating was under the control ofdiffusion process and electrochemical reaction both in Tafel region. And the limiting diffusionspecies was CuCl2-. Limiting current was dominated byC uCl2diffusion process and theessence of its generation mechanism was film dissolution mechanism dominated by mass transfer.In the high potential region (and below0.8V), CuCl film formed on the coating surface would notbe damaged or breakdown. The way of copper leaching of the coating was CuCl film dissolution,which could play a role of controlling the releasement of effective antifouling composition.Growth of current in high potential region relative to limiting current1was due to the oxidation ofC uCl2produced by dissolution of CuCl films. In the current growth stage of the high potentialregion, resulting from dissolution of CuCl films had three parallel competitivewhereabouts which were depositing into CuCl film again, oxidizing into Cu2+and diffusing tosolution bulk. In the limiting current2, the oxidation of was dominant. In the highpotential region, rate controlling step of electrochemical dissolution was the diffusion ofand Cu2+. Cold spray Cu-Cu2O coating had inhibitory effect on Navicula rows, Navicula parvaand Navicula pinna. The inhibition rate increased and the time of reaching100%inhibition ratedecreased with the increase of Cu2O component. For20%Cu2O-80%Cu coating and30%Cu2O-70%Cu coating, copper ion leaching rate has remained at50μg/(cm2d) above, the vastmajority of marine organisms could be inhibited from adhesion.The total copper leaching rate of the coating could be divided into two parts which wereelectrochemical dissolution of copper and chemical dissolution of cuprous oxide. Corrosionmicro-cell which promoted corrosion of the copper was formed by copper and cuprous oxidewhich play a role as cathode. The promotion was enhanced when dissolved oxygen content,salinity, temperature and immersion time increased. Increases in dissolved oxygen content, salinity, temperature and immersion time were conducive to electrochemical dissolution of copper andtotal copper leaching rate of the coatings. Leaching rate contribution ratio of cuprous oxide raisedas its content, salinity, immersion time increased and salinity, temperature, flow rate decreased.With the immersion time increased, total copper leaching rate decreased due to accumulation ofinsoluble products. Found in real sea environment experiments, the best coating in antifouling was30%Cu2O-70%Cu coating in each immersion time of1month,3months and13months. Throughanalysis of the experimental data, the antifouling effect of copper, copper alloys and antifoulingpaint which token cuprous oxide as antifoulant, due to corrosion of copper or dissolution ofcuprous oxide (film) which released soluble copper ions or cuprous ions, and the water layerwhich was rich in dissolved copper ions or cuprous ions formed and killed fouling organismscame close. In the cold spray Cu-Cu2O coating, cuprous oxide particles were different fromcuprous oxide film on the surface of the coating in structure, and the dissolution rate of the latterwas larger than the former, so the thinning process of the coating was controlled by the corrosionof copper.Application of Matlab2013b established a BP artificial neural network prediction system forcopper leaching rate of cold spray Cu-Cu2O coating in multivariate seawater environment. Thenetwork which architecture was5-28-1three-tier network structure token logarithmic S-typefunction (logsig) as hidden layer transfer function, linear function (purelin) as transfer function ofthe output layer and trainlm function as the training function. Training error goal was set to1×10-7and weights and thresholds of the network were initialized to zero before training. Experimentalresults shown that the neural network had good predictive ability and generalization ability toeffectively predict the copper leaching rate of cold spray Cu-Cu2O coating in multivariateseawater environment, and the prediction error was less than10%.Innovation of this paper is to:(1) The first application of cold spray technology to the field of pollution prevention openedup a new route for the future development of antifouling technology;(2) At present, the mathematical models for the electrochemical corrosion of copper onlyinvolved Tafel region and assumed that the diffusion process were control steps. In this paper, complete corrosion mechanism and corresponding mathematical model which contain the Tafelregion, limiting current region and the high potential region were established. Model buildingprocess in this paper without assuming that the diffusion process was controlled steps was betterto reflect the actual situation;(3) In this paper, the artificial neural network technology was applied to establish anprediction system for leaching rate of effective anti-fouling composition of the coating. Thesystem could accurately predict the copper leaching rate of the coating in marine environmentwith a variety of different factors such as dissolved oxygen, salinity, temperature and flow rate. |
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