| Hot dip aluminum coating is a simple and efficient surface coating technology combined with surface protection and surface strengthening,although the aluminum coating has some protection against the substrate,aluminum is a kind of self-passivated metal,and the corrosion is more serious.In recent years,the application of aluminum coating steel has been more and more extensive,and its resistance to pitting corrosion resistance has been proposed higher,the surface treatment of aluminum coated steel is a common technique in industrial production.This experiment adopts the sulfuric acid anodic oxidation process of hot dip aluminized layer of oxidation treatment,through SEM observation,XRD and EDS analysis,electrochemical corrosion test and other test means,to determine the best oxidation process parameters.Used nickel fluoride(NiF2),polytetrafluoroethylene(PTFE),nitrate cerium(Ce(NO3)3)sealed technology and organic acid(formic acid,oxalic acid,succinic acid),nickel sulfate modification technology of oxidation film were sesled treatment and modification,the best sealed and modification process parameters were determined.The effects of sealed treatment and modification on the corrosion resistance of oxide film were compared,and the optimum process parameters were determined.The main research contents and results are as follows:(1)The pore amorphous oxide film was obtained by using the oxidation process of sulfuric acid,the optimum technological parameters were 54g/L of sulfuric acid concentration and 30min of oxidation time.In this condition,the pore diameter of the prepared oxide film was small,the order of the pore was high,the thickness of the oxide film was large,it was 15?m,and the oxide film was the most dense.Best corrosion resistance.After oxidation,the breakdown potential was shifted 0.099V,and the corrosion sensitivity was reduced,and the difference between the breakdown potential and the protective potential is reduced by 0.098V,the re-passivation ability of the oxide film is enhanced and the degree of point corrosion is weakened.(2)The sealing agent does not enter the oxide film with the chemical reaction of the oxide film after sealed treatment.Instead,it is deposited in the surface pores,and the oxide film is still amorphous.PTFE has the strongest corrosion resistance in acidic,neutral and alkaline corrosive media.The oxidation film breakdown potential is moving 0.014V,the point corrosion sensitivity is reduced;The difference between the breakdown potential and the protective potential decreased by 0.053V,the reactivation ability of the oxide film was enhanced,and the point corrosion degree decreased.(3)After adding organic acid modified oxidation film,it is still amorphous state,but the organic acid will participate in the process of formation,succinic acid is the best organic additive,succinic acid modified the impedance of the oxide film by about 3 times;The breakdown potential of the oxide film is moving about 0.295V,which greatly improves the anti-corrosion resistance.The optimum concentration of nickel sulfuric acid was 3g/L,and the impedance of the oxide film was increased by about 5 times.The difference between the oxide film and the protective potential of nickel sulfate was reduced by 0.048V,but the corrosion sensitivity was stronger.The optimum membrane modification process for the membrane was succinic acid(20g/L).(4)Using PTFE sealed and succinic acid modification improves the corrosion resistance of oxide film,because of the modified aperture decreases,and the oxide film and passivation ability is abate,so the best process parameters of anodic coating is PTFE dispersion,25?,sealed 30 min,380? solidification 30min. |
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