Gravimetric Method for Hydrogen Evolution Measurements on Dissolving Magnesium

The determination of corrosion rate for Mg and Mg alloys by electrochemical methods is complicated by several factors, including the intense hydrogen evolution (HE) that accompanies Mg dissolution, so hydrogen gas collection is often used. In the present paper a new gravimetric method for hydrogen gas collection, originally developed by Curioni, is evaluated as an alternative to the common volumetric method. The gravimetric method is based on the buoyant force exerted by the H-2 produced by dissolving Mg when the gas is accumulated in a submerged container. The accuracy of the method is investigated using a Pt electrode and its suitability for the study of Mg corrosion behavior is examined using a high purity Mg specimen. The suitability of the new experimental set-up for the study of anodic HE (also termed Negative Difference Effect (NDE)) is also evaluated. The gravimetric method exhibits higher sensitivity to HE detection than the volumetric method both in the absence and in the presence of an external polarization. Real-time HE detection, during dynamic polarization was found to allow clear and rapid assessment of the effect of polarization on HE. Possible artifacts and experimental limitations of the gravimetric experimental method are discussed. (C) 2015 The Electrochemical Society. All rights reserved.