Anodic Spark Deposition from Aqueous Solutions of NaAlO ₂ and Na ₂ SiO ₃

Coatings were deposited on Cu ⁰ , Ni ⁰ , and Al ⁰ anodes from aqueous solutions of NaAlO ₂ and Na ₂ SiO ₃ by anodic spark deposition. Some coatings formed at constant current density (1.0 A/cm ² ) were characterized by scanning electron microscopy, electron beam microprobe analysis, X‐ray diffraction, and emission spectroscopy. A relation for the current decay during a multiple‐spark, constant‐voltage process was determined. This relation, which describes the behavior of most of the systems studied, is image where φ _t , φ ₀ , and φ _∞ are the current densities at time t , at the start of the decay ( t =0), and at the steady state, respectively. K is a constant that is voltage and system dependent.