Room-Temperature Electrochemical Healing of Structural Steel through Pulsed Plating and Tailored Electrolyte Chemistry

Abstract

Low-carbon steel is a widely used structural metal that, when fractured, can be repaired with high temperature processes such as arc welding. There are many applications, however, that would benefit from a room-temperature repair process which maintains the steel microstructure and prevents adjacent materials and electronics from overheating. We seek to enable effective room-temperature healing of steel using electrochemistry by understanding how ion transport and electrolyte chemistry influence growth and strength in fractured steel wires repaired with nickel electrodeposition. Experiments and simulations show that pulsed electroplating mitigates diffusion-limited growth to enable smooth and dense nickel deposits that have 4x higher adhesion to steel than nickel deposited by potentiostatic electroplating. We also investigate the effect of various nickel electrolyte chemistries on nickel-steel adhesion and the recovery of strength in healed steel. By combining pulsed electroplating with judicious use of electrolyte chemistry, fully fractured steel wires could be repaired to achieve up to 69% of their pristine strength.Finally, we propose a simple geometric model to estimate the energy and time requirements of electrochemical healing across length scales. Our model shows that if crack width can be minimized, over eight hundred 10-mm steel reinforcing bars (commonly used in construction) could be healed in under one minute using only one smartphone battery (5,000 mAh).This work is the first demonstration of electrochemical healing of a metal other than nickel (see our prior work: Hsain and Pikul, Adv. Funct. Mater. 29, 2019) and opens the possibility of healing a variety of structural metals using electrodeposition. With its low energy and time requirements, as well as its effective recovery of strength, electrochemical healing can be used to minimize weight in aerospace structures, extend the service life of structural parts, and more efficiently employ scarce resources in energy-constrained systems or remote environments.