Abstract
Abstract The corrosion properties inherent in oxide coatings formed on VT1-0 and VT5 grade titanium alloys affected by fast pulsed discharges under the process of microarc oxidation (MAO) have been studied both after sealing the coatings with polymers and with no sealing. The MAO coatings were formed in a pulsed mode, the duration of the anode current pulse amounting to 250 ± 25 μs, the duration of cathode current pulse being of 5 ± 0.5 ms, the pause between the anode and cathode current pulses amounting to 250 ± 25 μs, and the repetition rate of the anode and cathode pulses being of 50 ± 0.5 Hz. Alkaline solutions were used as electrolytes. Fluoroplastic and epoxy resin solutions were used to seal the oxide coatings. The obtained MAO coatings had 4.4–7.5% porosity in the case of the VT1-0 grade alloy and 5.4–12.1% porosity in the case of the VT5 grade alloy. The average pore diameter in the oxide coatings ranged from 0.1 to 0.5 μm. The XRD phase analysis has shown the fact that, in the composition of oxide coatings, there are anatase and rutile modifications of titanium dioxide. The corrosion testing performed using a 24% sulfuric acid solution at 40 and 75°C has shown that both oxide and oxide-polymeric coatings formed on the VT1-0 grade alloy are more corrosion resistant than similar coatings formed on the VT5 grade alloy. All the types of coatings formed on the VT1-0 alloy are corrosion-resistant at a testing temperature of 40°C. The sealing of MAO coatings with the use of polymeric materials improves their corrosion-resistant properties.