Electrolytic deposition of oxide coatings for solid oxide fuel cell interconnects

Composite yttria-silver coatings and praseodymia coatings were applied to 430 stainless steel by cathodic electrolytic deposition. Crack-free 0.5-1 μm thick coatings were obtained from chloride salts in aqueous or water-ethanol solutions. The electrical conductivity and oxidation behavior at 750°C of coated and uncoated samples were investigated. Coated samples oxidized for 24 h developed a scale thickness of approximately 1 μm and an area-specific resistance (ASR) of less than 0.1 ohm·cm², compared to uncoated samples which had a scale thickness near 1.3 μm and an ASR near 0.2 ohm·cm². The scale growth followed parabolic oxidation kinetics up to 168 h, spalling of the scale was evident. Another group of coated samples was initially heated in intermittent steps to 750 C over a period of hours. These samples showed better oxidation performance with good scale adhesion and had a scale thickness of less than 0.1 μm and an ASR of less than 0.1 ohm·cm².