Quantifying the influence of calcium ion concentration on the corrosion of high-purity magnesium, AZ91, WE43 in modified Hanks’ solutions

Abstract

The corrosion rate in a modified Hanks’ solution (containing no Ca ^2+ ions) was higher than in Hanks’ solution. The increase was by a factor of ∼12 for HP Mg and AZ91, and a factor of ∼6 for WE43. This quantitatively highlights the critical role of Ca ^2+ ions for Mg corrosion in synthetic body fluids. The Ca ^2+ ion containing solutions produced a dense corrosion-product layer of hydroxyapatite, Ca _3 (PO _4 ) _2 ) · Ca(OH) _2 , a greater fraction of which stayed on the corroding surface (∼0.2–0.3) compared with the Ca ^2+ ion free solutions which produced magnesium phosphate, Mg _3 (PO _4 ) _2 .

Keywords

• in vitro corrosion
• calcium ions
• magnesium
• weight loss
• simulated body fluid