Bipolar plates for electrolyzers made from stainless precision steel strip

Electrolyzers play a key role in the hydrogen economy, as they are responsible for converting green electricity into hydrogen. Applications range from residential and building systems to large-scale industrial use. The core component of an electrolyzer is a series of layered bipolar plates – the so-called stack. Depending on the application, these stacks can comprise up to 500 bipolar plates, as is the case in industrial electrolyzers. 

Materials engineer Jan Ullosat explains their function: “Bipolar plates are multifunctional elements. They conduct current between cells and feature ultrafine channels that transport water along with the process gases hydrogen and oxygen. They also help with thermal management. And they do this while simultaneously ensuring that the gases and liquid media remain completely separated at all times.”“

In the highly demanding production of bipolar plates, manufacturers use our stainless precision steel strip, primarily in the form of austenitic grades.

Each bipolar plate is formed with ultrafine indentations known as the flow field. The steel we supply for this purpose offers excellent forming properties. When two plates are then joined together, the recesses in the opposing plates form channels for transporting liquids and gases. To ensure these channels are completely leak-tight, our stainless precision steel strip must be manufactured within the tightest tolerances to be perfectly flat. 

As Ullosat explains: “We achieve a thickness tolerance of +/- 0.020 millimeters (0.0008”), for example, even though the standard for this material as wide strip specifies +/- 0.055 millimeters (0.0022”). That means we come in at less than half the standard’s precision class specification – and do so consistently across the full width and entire length of the strip.”  

If the thickness tolerance or taper is off on even a single bipolar plate, there is a risk of that cell leaking, which will render the entire stack unusable. By meticulously maintaining defined parameters across all production batches, we offer our customers a high degree of reproducibility for a highly reliable manufacturing process. Another aspect that sets us apart is that we manufacture our materials in accordance with the Pressure Equipment Directive for higher pressures of 20 to 30 bar – and we’ve even received certification in this regard.

“Our customers coat the surface of the bipolar plates to optimize electrical performance based on the electrolyzer’s design. In this context, the coating requirements are highly individual,” Ullosat explains. Such customer-specific coatings require a correspondingly customized surface structure, as the requirements for adhesion and uniformity, for example, can vary significantly. Here too, we offer our customers the best possible foundation. Ullosat explains: “We have the expertise to precisely tailor the surface topology of all our materials to our customers’ exact specifications. This is how we help ensure that our customers can optimize the plate coating – and ultimately the performance of the stack – to their full potential.”