Polymer gel as a model to evaluate the corrosion protection of metals' stability

Corrosion testing of some medical alloys is carried out in solutions that have a similar composition to some liquid medium in the human body. However, if these alloys are located in a production environment they come in contact with not only some liquid medium but polymeric molecules, muscle tissue, and bone tissue. We can conceive of the environment as a gel: some liquid is distributed into the solid framework. The gel involves the functional groups that are similar to those in humans. The presence of a liquid phase in the polymer gel allows involving different modifiers in the polymer matrix and varying them over a wide range and changes in properties. The polymer film can be fixed on the surface with any shape and size due to adhesion. The work investigated the possibility of using gels based on methacrylic copolymers for evaluating the corrosion resistance of commercially pure titanium of the brand VT 1-0 and the alloy of the brand VT6 with some coatings of SiC, TiB2, and ZrO2. There are two techniques for the evaluation of corrosion resistance: The first method is to test some morphological changes on the alloy surface after contact with the gel over 7 days and months. It can be traced by observing some changes in the craters’ shape and microformations that are present on the metal surface after doping. Based on our results, we divided the metals into three groups according to their chemical corrosion resistance in the gel. The first group is metals that changed in surface morphology after 7 days’ exposure to the gel. We could observe the removal of dark micropoint, the increase and deepening of some craters, and a more distinct appearance of the boundaries of built-up layers on the alloys’ surfaces. This group included VT1-0, VT1-0 doped with TiB2, and VT6 doped with SiC. The second group of alloys had the same changes in morphology after a month. This group included the alloys VT6, VT1-0 doped with SiC and VT1-0 doped with ZrO2. On the surfaces of the alloys of the third group, some changes were absent after the exposure. This group included alloys VT6 doped with ZrO2 and VT6 doped with TiB2. The second technique is to register corrosive charts in a cell where the polymer gel is used instead of a liquid. The corrosion currents of the metals before and after the doping showed that the modification of metal surfaces was high-performance only for silicon carbide. It was found that the use of titanium boride for doping the VT1-0 surface and zirconium oxide for doping the VT6 both reduced metal resistance to galvanic corrosion. The analysis of consecutive polarization curves revealed that the resistance to prolonged electrochemical corrosion of VT1-0 increased if we use silicon carbide and zirconium oxide as a coating for covering.

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