CORROSION RESISTANCE OF Ti AND ITS ALLOYS IN SEAWATER

摘要

Titanium and its alloys are used widely for making of ships and submarines so study ofrntheir corrosion resistance in natural sea media is very important. Additives of Si, Al, Zrrnand Nb increase mechanical characteristics of titanium. The influence of Si, Al, Zr andrnNb on corrosion behavior of titanium in chloridcontaining media is studied not enoughrnup to now. The aim of the present work is to study corrosion behavior of titanium andrnits alloys alloyed with additives of Si, Al, Zr and Nb in sea water.rnCorrosion behavior of titanium alloys of eutectic structure as cast and deformedrncontaining (2-6) wt.% of Si, (2-6) wt.% of Si + 3 wt.% of Al, and (2-6) wt.% of Si + 3rnwt.% of Al + 6 wt.% of Zr or Nb in sea water (Black sea, Crime, Ukraine) atrntemperature 295 K have been studied. Corrosion and electrochemical investigationsrnwere carried out by gravimetric method. Titanium VT1-0 (technical titanium) was usedrnas standard specimen. All specimens under study were sandpapered, washed in ethylrnalcohol and distilled water. Then the specimens were weighed and immersed into searnwater where they stayed for 40 days. After that these specimens were took out from searnand weighed again. Corrosion rates calculated in mm year-1rnThe results of carried out investigations showed that all alloys were stable in sea water.rnThe total corrosion rates of all investigated specimens changed within the limits ofrn0.001-0.100 mm year-1. It was established that total corrosion rates of Ti-Si alloysrncoincide with the corrosion rate of VT1-0 practically. The corrosion rates of the alloysrnof Ti-Si-Al and Ti-Si-Al-Zr (Nb) systems as cast were in 10-20 times less in comparisonrnwith the corrosion rate of titanium VT1-0. Besides, total corrosion rates of deformedrnalloys of Ti-Si-Al-Zr (Nb) system were in 10-20 times less in comparison withrncorrosion rates of alloys as cast of the same chemical compositions. High concentrationrnof active centers on the surface of deformed alloys facilitates their passivation in searnwater. Increase of the strength of connection of titanium atoms with oxygen of waterrnbecause of improvement of forming of active centers on the surface of deformed alloysrnresults in producing of close passive film which protects deformed alloys better thenrnpassive films forming on the alloys as cast of the same chemical composition.rnThus, stand investigations of corrosion resistance of technical Ti and alloys of Ti-Si, Ti-rnSi-Al and Ti-Si-Al-Zr ( Nb) systems in sea water were carried out. The total corrosionrnrates of titanium VT1-0 and its alloys in sea water were found. It was established thatrncorrosion resistance of alloys of Ti-Si system and VT1-0 as cast coincided practically.rnTotal corrosion rates of deformed alloys of Ti-Si-Al-Zr (Nb) systems in sea water werernlower in 10-20 times then those of alloys as cast of the same compositions.