Open-circuit potential as an indicator of damage of atomic layer deposited TiO2 on AISI 304 stainless steel

An experimental method is presented for the determination of the extent of damage of photoactive titanium dioxide (TiO2) coatings on stainless steel substrate by measurement of open-circuit potential (OCP) during the deformation of a coated specimen under UV illumination. 50 and 100 nm anatase and 100 nm rutile TiO2 coatings were produced on AISI 304 stainless steel substrate using atomic layer deposition. The photoactivity of the coatings was confirmed by the measurement of OCP under periodic UV illumination. The changes in the OCP of 50 nm thick anatase coating observed during the tensile tests with UV illumination indicated that the onset of cracking of the coating occurred at 1.1% engineering strain and that about 70% of the coating was detached at 16% strain. 100 nm anatase coating exhibited similar behavior. Small changes in the OCP of 100 nm rutile coating up to 30% strain indicated considerably smaller detachment of the coating.