Corrosion Properties of Electrodeposited Thin Coatings of Polycrystalline Silver

Abstract

For polycrystalline silver coatings electrodeposited from electrolytes based on different Ag(I) coordination compounds such as [Ag(CN)2]−, [Ag(CN)3]2−, [Ag(SCN)4]3−, [Ag(CN)2(SCN)2]3−, and [Ag(SO3)2]3− at current densities of 2.5 to 75 mA⋅cm−2, we have established a relationship between the corrosion parameters of these deposits determined by the methods of electrochemical impedance spectroscopy and voltammetry and their crystalline roughness (uniformity at the nanolevel). We have also established that, with decrease in the surface roughness of an electrolytic silver deposit (R a ∼ 40–80 nm), the corrosion resistance increases. In this case, as the surface roughness increases by 20 nm, the corrosion resistance is halved, and the resistance to a corrosive medium decreases noticeably, though the deposit is uniformly distributed over the thickness on the microprofile. For silver coatings with the same true surface area, the larger the mean roughness R a , the larger the corrosion rate, independently of the texture of the deposit and deposition conditions.