Acid Pickling/polishing of AZ31 Magnesium Alloy

Abstract

This article reports a new chemical bath for preparing a mirror-like surface of AZ31 Mg alloy. In order to find an appropriate chemical polishing solution, four different acidic solutions of sulphuric acid, nitric acid, acetic acid and a specially designed mixture of nitric acid and acetic acid were investigated in view of the changes in surface appearance, roughness and dissolution rate of AZ31 Mg alloy. The surface scales on AZ31 Mg alloy were readily removed by all the acidic solutions, but a reflective surface was produced only by etching in the specially designed solution, and only after a specific etching time. The surface roughness increased with etching time in sulphuric acid, nitric acid, and acetic acid, but it lowered after a specific etching time in the specially designed mixture of nitric acid and acetic acid. Dissolution rate of the alloy in the specially designed mixture of nitric acid and acetic acid appeared to be more than twice than that in separate nitric acid or acetic acid. In this work, we recommend the mirror-like surface of AZ31 Mg alloy obtained by polishing for an optimum time in a mixture of nitric acid and acetic acid for following surface finishings, chemical conversion coating, electroplating, electrophoretic painting and anodizing treatment.

Effect of Fluoride Conversion Coating on the Corrosion Resistance and Adhesion of E-painted AZ31 Magnesium Alloy

“…The tape-masked AZ31 Mg alloy samples were degreased for about 10 min in 1 M NaOH and then for about 5 min in acetone. The samples were then chemically polished in a specially designed solution [11]. Cerium conversion coatings were obtained by immersing the chemically polished samples in 500 ml of 0.025M Ce(NO 3 ) 3 .6H 2 O solution for only 30 s as longer treatment time produce thicker cerium conversion coatings that exhibit poor adhesion with E-paint.…”

Investigation of Chemical Mechanical Polishing Slurry of magnesium alloy

“…in recent years by virtue of its excellent high quality and efficiency, ultra-low damage, and stable effect. Song [5] and Zhou [6] et al developed chemical polishing solutions for magnesium alloys containing phosphoric acid, and Fazal [7] et al developed a chemical polishing solution for magnesium alloys consisting of nitric acid and acetic acid. Chemical polishing often adds some environmentally polluting reagents to obtain high material removal rate and surface quality, such as strong acids, strong bases, chemical reagents containing sulfur and phosphorus.…”