Influence of pre-treatment on zirconium based conversion coating on AA2024

Abstract

A comparison of the influence of two alloy pre-treatments and temperature treatments on the formation and composition of zirconium based conversion coating on the AA2024 alloy has been performed. The investigation employed mass changes, atomic force microscopy (AFM), XRD dispersive spectroscopy (EDX), infrared spectroscopy (IR) and electrochemical tests by open circuit potential (OCP) measurements. Pre-treatment using only alkaline etching is called alkaline pre-treatment. When alkaline etching is followed by de-oxidization in a phosphoric acid solution the process is called acidic pre-treatment. Conversion coatings were formed in Pragokor BL. IR analysis revealed the formation of a phosphate on the alloy surface. EDX analysis showed Mg dissolution. The Zr content increased with the temperature of the conversion coating formation. Both pre-treatment methods provided a phosphate layer on the alloy surface.

Effect of Micro-Zone pH Gradient on AM60B Vanadate Film and Corrosion Behavior

“…The vast majority of chemical conversion processes have attracted much attention due to their simple operation, energy saving, environmental protection and economy. In addition, their application in coloring decoration and electroplating pretreatment has been practically applied [4,5]. However, the research on the chemical conversion of magnesium alloys started relatively late [6].…”