Corrosion inhibition induced by captopril in Hanks’ solution on bioresorbable Mg–Zn-(Y, Nd) alloys fabricated by powder metallurgical technology

Abstract

Mg–Zn alloys containing rare-earth elements (REEs) have been regarded as potential candidates for bioresorbable stent materials. As implanted in coronary arteries, stents could be exposed to angiotensin-converting enzyme (ACE) inhibitor drugs that are widely used for post-percutaneous coronary intervention patient therapy. This work investigates the inhibitory effect of an ACE inhibitor drug, namely captopril, on the corrosion behavior of Mg–Zn-(Y, Nd) alloys in Hanks' solution. Three alloy compositions, namely Mg–1Zn-2.9Y, Mg–5Zn-1Nd, and Mg–2Zn-0.2Y-0.5Nd, were prepared by a powder metallurgical (PM) method. The corrosion behavior and inhibition efficiency were studied using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), Mott-Schottky analysis, and a hydrogen evolution test. It is shown that captopril suppressed the dissolution kinetics of Mg–Zn-(Y, Nd) alloys in Hanks' solution. The captopril inhibition efficiencies (η) for the alloys are in the order of Mg–2Zn-0.2Y-0.5Nd > Mg–5Zn-1Nd > Mg–1Zn-2.9Y. A remarkable η of 48.4 % has been achieved for the Mg–2Zn-0.2Y-0.5Nd alloy. The EIS results revealed that the polarization resistance increased in the alloys after the addition of captopril to Hanks' solution. The Mott-Schottky analysis showed that the Mg–Zn-(Y, Nd) alloys behaved as an n-type semiconductor but switched to a p-type for the Mg–1Zn-2.9Y alloy in the captopril-containing Hanks’ solution. The surface analysis of the post-corrosion-tested sample has observed captopril film partially covering the α-Mg matrix, which acted as a protective layer against corrosion.