The effect of extension twinning on the electrochemical corrosion properties of Mg–Y alloys

•{101¯2} extension twins form in a Mg–1wt.% Y alloy with a true strain of 1%.•Extension twins improves electrochemical corrosion properties of a Mg–1wt.% Y alloy.•{101¯2} twins vary pitting potential, film formation and charge transfer resistance.•The reasons root in a preferential oxide layer and low twin boundary energy.