Physicochemical properties of Mn1.45Co1.45Cu0.1O4 spinel coating deposited on the Crofer 22 H ferritic steel and exposed to high-temperature oxidation under thermal cycling conditions

Abstract

The Crofer 22 H ferritic steel substrate was coated with an Mn1.45Co1.45Cu0.1O4 spinel by means of electrophoresis. After high-temperature oxidation under thermal cycling conditions, the physicochemical properties of the obtained system were evaluated. During 48-h cycles that involved heating the samples up to temperatures of either 750 or 800 °C, the oxidation kinetics of both coated and unmodified steel approximately obeyed the parabolic rate law. The unmodified steel was oxidized at a higher rate than the system consisting of the substrate and the coating. In its bulk form, the spinel consisted entirely of the cubic phase and it exhibited high electrical conductivity. The Mn1.45Co1.45Cu0.1O4 coating, on the other hand, was compact and consisted of two phases—the cubic and the tetragonal one—and it was characterized by good adhesion to the metallic substrate. After cyclic oxidation studies conducted for the two investigated temperatures (750 or 800 °C), the coating was determined to provide a considerable improvement in the electrical properties of the Crofer 22 H ferritic steel, as demonstrated by the area-specific resistance values measured for the steel/coating system. The evaporation rate of chromium measured for these samples likewise indicates that the coating is capable of acting as an effective barrier against the formation of volatile compounds of chromium. The Mn1.45Co1.45Cu0.1O4 spinel can therefore be considered a suitable material for a coating on the Crofer 22 H ferritic steel, with intermediate-temperature solid oxide electrolyzer cells as the target application.

Thermal Sprayed Protective Coatings for Bipolar Plates of Hydrogen Fuel Cells and Water Electrolysis Cells

“…Ferritic stainless steels containing 17-25 wt.% Cr (e.g., Crofer 22 APU, SUS 430 and 441, SMG 232) are often used as BP substrate materials for SOFCs and SOECs due to appropriate CTE, excellent mechanical properties and high electrical conductivity [50,59,60]. FSS BPs are exposed to both reducing atmospheres (SOFC anode and SOEC cathode) and oxidizing atmospheres (SOFC cathode and SOEC anode) [61,62] during the cell operation. Oxidation corrosion of FSSs mainly occurs in the oxidizing atmosphere to form metal oxides (such as Fe 2 O 3 , Cr 2 O 3 and MnCr 2 O 4 ) [63][64][65][66], resulting in performance degradation and lifeshortening of SOFCs and SOECs.…”

The Preparation and Properties of Ti(Nb)-Si-C Coating on the Pre-Oxidized Ferritic Stainless Steel for Solid Oxide Fuel Cell Interconnect

“…The solid oxide fuel cell (SOFC) is an electrochemical device that can convert chemical energy directly into electricity and heat without combustion or mechanical processes [1][2][3]. It has gained significant attention due to the advantages of high efficiency, fuel flexibility, and low production of pollutants.…”

Review—(Mn,Co)3O4-Based Spinels for SOFC Interconnect Coating Application

“…Similar increases in oxidation resistance of the interconnect alloys have been reported for Cu-doped MCO coatings in addition to bolstered electrical performance. 96,97 Additionally, as the cationic distribution present in the cubic phase allows for electrical conductivity 1-2 orders of magnitude higher than that of the tetragonal phase, the stabilization of the cubic phase reported for MCO coatings with Fe or Cu additions 37,[66][67][68][69][70][71] is highly desirable from an electrical standpoint.…”

“…have been produced by various deposition techniques, such as slurry coating (e.g., brush painting, wet powder spray, dip coating, and screen printing), 33,35,[106][107][108][109] thermal spray, [110][111][112][113][114][115][116][117] physical vapor deposition (PVD) (e.g., electron beam PVD, EBPVD, thermal evaporation, sputtering, etc. ), [118][119][120][121][122] electrodeposition, [123][124][125][126][127] electrophoretic deposition (EPD), 95,97,126,[128][129][130][131][132][133] etc. The choice of deposition techniques mainly depends on the coating composition/ thickness, surface topography of the interconnect, and cost of equipment.…”

“…A relatively dense and crack-free MCO spinel coating was formed on the substrate surface through EPD of the precursor layer followed by the reduction/reoxidation steps with a re-oxidation/sintering temperature of 900--1000 °C. 95,97,126,[129][130][131][132][133]160 Talic et al compared the coating quality of an EPD-processed MnCo 1.7 Fe 0.3 O 4 coating after different sintering processes. 161 As schematically shown in Fig.…”