ChromLokTM coatings provide oxidation protection to ferritic alloys while maintaining excellent electrical connectivity at high temperatures.
While other corrosion protection methods (silica- or alumina-forming alloys) create oxidation resistant surfaces, contact resistance is increased. ChromLokTM surfaces remain electrically conducting for years under harsh temperature conditions.
Nexceris has developed the ChromLokTM family of oxide based high temperature protective coatings to limit corrosion and improve the stability of metallic components in harsh process environments. These crystalline oxide coatings are unique in that they achieve excellent adhesion and chemical compatibility with common stainless steels through a simple manufacturing process.
Nexceris offers multiple proprietary formulations in the ChromLokTM family to meet your needs. Leveraging world-class capabilities, we produce unique ceramic oxide powders to tailor the process and properties of each coating. Through careful design of the oxide coating suspension, the microstructure and performance of the resultant coating can be optimized. The coating can also be applied in localized areas on complex geometries to create high-value solutions.
Nexceris has developed carefully controlled sintering processes to achieve high density oxide coatings on metal substrates. The image below shows the top-down and cross-section microstructure of a ChromLokTM manganese cobaltite (Mn,Co)3O4 mixed spinel oxide coating on a ferritic stainless steel (441) substrate. The manganese cobaltite (MCO) coating was deposited on the stainless steel substrate through an aerosol-spray deposition (ASD) process, followed by heat treatment to develop a dense protective coating.
SEM images of MCO coating, applied using Nexceris’ coating process: (a) top-down image (left); and cross-section image with superimposed EDS compositional analysis (right).
Oxidation resistance of ChromLokTM coated and uncoated 18 Cr ferritic stainless steel.
Nexceris’ oxide coatings demonstrated excellent long-term stability at elevated temperatures. The above image shows the oxidation resistance of a 18 wt. % Cr ferritic stainless steel substrate with and without an MCO protective coating at 800 °C and 900 °C. The ChromLokTM surface serves as an adherent oxygen diffusion resistance layer, limiting the growth of the inherent alloy oxidation products at the surface, and preventing loss of Cr.
In addition to demonstrating excellent high temperature stability in both oxidizing and reducing environments, the MCO coating is electrically conductive. Figure 4 shows the long-term electrical resistance (ASR) of MCO coated stainless steel in humidified air at 800 °C. Even after 35,000 hours of service, the coating has maintained extremely low resistance.