High Anticorrosion Nano Zn-Fe Coatings by Pulse Electrodepositing

摘要

Nano Zn-Fe coatings in a chloride electrolyte with additives by reverse pulse current were obtained and the anticorrosion was investigated. The morghology and crystal size of Zn-Fe alloy depositions were measured by scanning electron microscope and atom force microscope. Coatings with 30 nm or so crystal size was obtained with mean current density 9.0 A·dm~(-2), duty cycle 60%, frequency 500 Hz and time of negative to positive 30 ms: 8 ms. It was detected by X-ray diffraction that the pulse plated coatings of Zn-Fe were mixtures of two phases, one of them being the α-phase and the other pure zinc or the α-phase with a significantly lower proportion of Fe. The pulse plated Zn-Fe coatings' corrosion resistance was greatly improved compared with Zn-Fe coatings by direct current according to Tafel tests, saline immersion and salt spray tests. The anticorrosion of Zn-Fe coatings with 30 nm crystal size was 2～3 times than that of normal Zn-Fe alloy deposits.