| The optimum formula and concentration range of the main ingredients additivesfor TC1 and TC4 titanium alloy were deterimined. The effects of technologyparameters, such as temperature, agitation on corrosion processing rate, surfacequality, and processing accuracy were discussed. The analysis methods of main ionsin bath solution were improved, in order to analysis steps simplify and reduce errors.The life span of corrosion processing solution and the controlling means of bathsolution within life-cycle were explored. Meanwhile the morphologies of titaniumalloy after corrosion processing were observed. Furthermore the corrosion dissolutionmechanism and the dynamics low were studied by E-t and polarization curves.The main constituents of precise corrosion processing solution are HF 100mL/L,HNO3200mL/L, HA0.2g/L, HN2.5mL/L, and the concentration range of the bulksolution are HNO3120~300mL/L, HF60~125mL/L, HNO3-HF volume ratio are1.5~2.5, HA0.1~0.3g/L, HN 1.5~3.5mL/L. The concentration of HF, HNO3-HFvolume ratio are the key influencing factors of corrosion processing rate, surfacequality, and processing accuracy. With the increasing of HF concentration, thecorrosion processing rate increase, but surface quality, processing accuracy reduce,and the etching ratio increase. When the ratio of HNO3 and HF increases gradually,the corrosion rate initially increased and then decreased, meanwhile HNO3 cansignificantly reduce surface roughness. Mixed-type additives HA and HN caneffectivelyimprove accuracyof processing and surface qualityof sepcimen.The temperature is an important factor for corrosion processing. With theincreasing of temperature the corrosion processing rate and the etching ratio increase,while surface quality and processing accuracy reduce. The temperature of bathsolution was controlled between 30±2℃. In the optimum formula, the total reactionheat released of TC1 and TC4 titanium alloy are respectively 12180J and 13650Jduring 70min. Periodical turnover is more favourable to improve surface quality andprocessing accuracy for the vertically hanging specimen. The optimum location ofagitator is placed in parallel with the specimen center and at 200mm away from thespecimen.The H+analysis of steps are simplified. The standard curve is produced and Ti4+ismasked before the measurement of NO3- every time. In the course of the analysis of Ti4+a blank solution was used for test Ti4+concentration. Solution is diluted 103times,and the pH is controlled between 5~6 when testing the concentration of F-. 50mL/LHF, 30mL/L HNO3, additives of one-half of initial volume are added to solution whenthe quantity of titanium ions increased about 10g/L. The life span of bath solution ofTC1 andTC4 titanium alloyare 90.26 g/Land 71 g/Lrespectively.The corrosion procession rates of bulge and the pit are not the same. Thespecimen surface become uneven clearly in the solution containing only HF, but thesize and the depth of pit decreased after HNO3 added thatresults from the surfacepassivation of sepcimen. With the concentration increaseing of HNO3, the ratedifferential valume between the pit and bulge lessens, and specimen surface becomesmore even. In case of HF solution with low concentration, the polarization curves oftitanium alloy take on obvious active-passive transition characteristics. In case of HFsolution with high concentration, when HNO3 increase to a certain value, thepolarization curves show the self-passivation. When volume ratio of HNO3-HF is 2:1,corrosion potential of titanium alloy is the most negative, the maintaining passivitycurrent density and potential are the greatest, and corrosion processing rate reachs themaximum. Ahead dozens of seconds in corrosion processing, corrosion potentialsharply becomes negative, the corrosion processing rate is bigger. The passsive filmwas attacked quickly by HF, then the surface be passivated by HNO3, the corrosionpotential rises. When the formation of passive film and dissolution of the matrixachieved dynamic balance, corrosion potential and corrosion processing rate tend tobe stable.
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