A method for applying a coating to a defect area of a reactor component includes forming a patch on the reactor component at the defect area using a plasma-spray coating process. The plasma-spray coating process includes grounding the reactor component and a power supply of a plasma gun to a common ground such that a potential difference exists between the reactor component and a cathode of the plasma gun, and concurrently directing an ion-etching stream and a coating stream towards the region of the reactor component using the plasma gun while maintaining a desired distance between the plasma gun and the region of the reactor component. The directing the ion-etching stream includes heating the region of the reactor component using a plasma stream exiting a spray nozzle of the plasma gun. The coating stream includes droplets of a coating material.