Recycled cobalt from spent Li-ion batteries as a superhydrophobic coating for corrosion protection of plain carbon steel

A new recycling and film formation scheme is developed for spent Li-ion batteries, which involves the combination of ascorbic-assisted sulfuric leaching and electrodeposition to fabricate a corrosion resistance superhydrophobic coating. The idea behind the simultaneous use of sulfuric and ascorbic is to benefit from the double effect of ascorbic acid, as a leaching reducing agent and as morphological modifier during electrodeposition. Quantum chemical calculations based on the density functional theory are performed to explain the cobalt-ascorbate complexation during the electrocristalization. The optimum parameters for the leaching step are directly utilized in the preparation of an electrolyte for the electrodeposition process, to fabricate a superhydrophobic film with a contact angle of > 150° on plain carbon steel. The potentiodynamic polarization measurments in 3.5 wt % NaCl showed that boric-pulsed electrodeposited cobalt film has 20-times lower corrosion current density and higher corrosion potential than those on the non-coated substrate.