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This work investigates the oxidative stability and corrosivity of residual cooking oil (RCO) methyl biodiesel exposed to metallic coupons (copper and carbon steel) under simulated storage conditions (static immersion for 90 days within closed vessels) and the effect of antioxidants (tert-butylhydroquinone, curcumin, propylgallate, and butyl-hydroxyanisole) on biodiesel and metallic surfaces. The induction period measured during the experiment showed that all antioxidants retarded biodiesel degradation due to their antioxidant properties. Scanning-electron microscopy and X-ray diffraction of the metallic surfaces revealed the presence of oxides due to the corrosion by biodiesel in absence of antioxidants. Nevertheless, the presence of carbonaceous solids over the metallic surfaces was found which evidences the anticorrosive properties of the antioxidants, confirmed by X-Ray spectroscopy that showed increase in the content of carbon and oxygen on the surfaces. Measurements of corrosion rate also confirmed the anticorrosive action of all antioxidants. Hence, this work shows the dual properties of antioxidants acting as free radical scavengers in the RCO biodiesel as well as corrosive inhibitors, with a special performance of propylgallate, probably due to the presence of more hydroxyl groups in its structure that also may facilitate its interaction with the metallic surface. • Free radical scavenging and corrosion inhibition by antioxidants in biodiesel from residual oil. • Immersion tests using copper and carbon steel coupons prove this dual effect of antioxidants. • Higher induction period values by propyl gallate (PG) in biodiesel exposed to both metals. • PG also showed higher anti-corrosive properties in this biodiesel under simulated storage. • Protective layers of carbonaceous solids over metals were formed in biodiesel with antioxidants. [ABSTRACT FROM AUTHOR]