Production process for Sandvik's coated steel strip
We have developed a PVD (physical vapor deposition) process with roll to roll type continuous evaporation coating of full-width strip steel. Our industrial-scale process significantly shortens the value chain for bipolar plate production. It also ensures homogenous coating of the whole strip surface and repeated quality from batch to batch.
Advanced coatings (within nanometer range) with multiple-layer options are applied to a strip in motion. The pre-treatment ensures a clean metallic surface, with good adhesion between the substrate and the coating. All coatings are characterized by very low content of impurities and foreign elements. The coating process also assures close thickness tolerances of the surface layer.
The surface layers consist of metallic elements, for example, aluminium (Al), nickel (Ni), cobalt (Co), or tin (Sn). Non-metallic coating in the form of carbon (C) is offered for low-temperature fuel cell bipolar plate material.
Environmentally friendly process
Sandvik's coating technology is environmentally friendly, with no discharge to water or air and no toxic residues. The coating process is also energy efficient compared to electroplating, which consumes approximately 60% more energy.
Stainless steel is an environmentally friendly process, as it is manufactured using mainly recycled materials.
1. Pre-treatment (surface inspection, cleaning)
A clean surface is a prerequisite for good adhesion. To detect eventual harmful defects, the surface is inspected visually using a camera system.
2. PVD coat (in-line pre-treatment, coating)
After a surface conditioning step, the surface is coated using a continuous physical vapor deposition process.
3. Quality control (coating thickness, coated surface inspection)
The surface coating thickness is constantly measured in-line with the use of integrated coating specific devices. To detect eventual harmful defects, the coated surface is inspected visually.
4. Finishing steps
After coating, the coil is tested according to internal and external specifications and slit to final width. Prior to shipping, the coil is packed in a suitable box.