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Objectives

Cobra targets

The COBRA project aims at establishing best-of-its-class stack hardware for automotive application. In the scope of Fuel Cell and Hydrogen Joint Undertaking (FCH JU) objectives as shared in 2013 Annual Implementation Plan (AIP) [1], Cobra project will focuses on the following targets:

  • Development of corrosion resistant conductive coatings for low cost metals, including verification of ageing behavior,
  • Modeling and quantification of levels of corrosion products, including assessments of their potential contamination on other components (for example Membrane Electrode Assembly – MEA),
  • Development of cost effective metallic bipolar plate manufacturing technologies,
  • Demonstration of metal/coating combination manufacturing,
  • Cost reduction potentials of bipolar plates for different production volumes

Important specifications

The COBRA project aims at establishing best-of-its-class stack hardware for automotive application. The general work flow will therefore be oriented along the typical automotive development cycle. Multiple coatings will be developed and characterized following this cycle in automotive and marine conditions, including in-field testing.

Project results will be evaluated considering durability, contact resistance, corrosion resistance and price of those coatings solution as shown in the shared coating selection matrix.

Cobra methodology will use GO / NO GO milestones (indicated in the following table) to assure complete objectives achievement.

New coatings

COBRA will improve individually a number of techniques and approaches for the development of practical, low cost, high-performance and durable coatings.

Pulse plating coating

One of the goals of COBRA is the development of a pulse plating process for the electrodeposition of gold, silver and/or nickel coatings among others, with the purpose of obtaining highly uniform layers, improving the properties of the conventional gold plated stainless steel bipolar plates and, thus, able to be a suitable alternative to gold plated steel.

figure-1

The experimental work will be focused on the development and optimization of a process for pulse plating metals on stainless steel bipolar plates to obtain high quality coatings of low ICR values as required by fuel cell industry. The optimization of forward-reverse cycling will allow the tailoring of the roughness, the uniformity and conformability of the obtained coatings. The pulse plating bath composition will also be studied and optimized to obtain the best performance.

As Au is a very expensive metal, COBRA also envisages the development of protective coating systems consisting of a pulse plated non-noble metal underlayer and a sol-gel topcoat.
figure-2

Sol-Gel coating

Among sol-gel applicable formulations, various metal oxides and alkoxides will be used as precursors in order to modifying Si, Zr or Ti based matrix formulations and create new chemically resistant and conductive sol-gel layers. If necessary, anticorrosive species such organic inhibitors and/or metal oxide nano/micropowders will be embedded into the matrix in order to provide the coating with the necessary anticorrosive capacity and improve the durability of the protective system.

PVD coating

PVD coated ceramics based on transition metals are considered to have sufficient surface properties for the fuel cell environment. The Ceramic MaxPhase concept developed by Impact Coatings provides a beneficial starting point. The concept has shown to provide good electrical and corrosion properties for various bipolar plate designs. Much development remains for optimal coatings for different materials and shapes of the plates, work that requires co-operation involving research, manufacturers, and final users of bipolar plates. Furthermore, PVD development for bipolar plates has focused on the coating properties, while productivity aspects for volume production needs to be further explored.