Evaluation of CoBlast Coated Titanium Alloy as Proton Exchange Membrane Fuel Cell Bipolar Plates

Abstract

We investigated the potential of graphite based coatings deposited on titanium V alloy by a low-cost powder based process for bipolar plate application. The coatings which were deposited from a mixture of graphite and alumina powders at ambient temperature, pressure of 90 psi, and speed of 20 mm were characterised and electrochemically polarised in 0.5 M H 2 SO 4 + 2 ppm HF bubbled with air and hydrogen gas to depict the cathode and anode PEM fuel cell environment, respectively. Surface conductivity and water contact angles were also evaluated. Corrosion current in the 1 A/cm 2 range in both cathodic and anodic environment at room temperature and showed negligible influence on the electrochemical behaviour of the bare alloy. Similar performance, which was attributed to the discontinuities in the coatings, was also observed when polarised at 0.6 V and −0.1 V with air and hydrogen bubbling at 70 ∘ C respectively. At 140 N/cm 2 , the coated alloy exhibited contact resistance of 45.70 mΩ⋅cm 2 which was lower than that of the bare alloy (66.50 mΩ⋅cm 2 ) but twice that of graphite (21.29 mΩ⋅cm 2 ). Similarly, the wettability test indicated that the coated layer exhibited higher contact angle of 99.63 ∘ than that of the bare alloy (66.32 ∘ ). Over all, these results indicated need for improvement in the coating process to achieve a continuous layer.

Ex-situ evaluation of PTFE coated metals in a proton exchange membrane fuel cell environment

“…Therefore, a considerable amount of research has investigated the corrosion behaviour of metal alloys such as stainless steel (SS) [11], [13]- [18], titanium (Ti) [19]- [21], and aluminium (Al) [22], [23]. SS alloys have been considered as the reference materials for metal bipolar plates [11], [24]- [26].…”

Assessment of Carbon-Titanium Multilayer Coatings on Aluminum as Bipolar Plates in PEM Fuel Cells

“…Traditionally, graphite was the main choice for the bipolar plate fabrication due to its conductivity and high corrosion resistance in the working environment of fuel cells. However, gas permeability, low mechanical strength and the expensive machinery cost hindered its application in the fuel cell technology [8,[13][14][15]. Metallic materials like stainless steel and titanium have been proposed as bipolar plate materials because of their gas impermeability, high mechanical strength, high thermal and electrical conductivity [3,4,13].…”

“…However, gas permeability, low mechanical strength and the expensive machinery cost hindered its application in the fuel cell technology [8,[13][14][15]. Metallic materials like stainless steel and titanium have been proposed as bipolar plate materials because of their gas impermeability, high mechanical strength, high thermal and electrical conductivity [3,4,13]. Nevertheless, the high weight of stainless steel and expensive and time consuming machinery of titanium (because of its inherent hardness) as well as the corrosion of these metals necessitate finding another alternative material for the bipolar plates [16].…”

“…17 Aluminum can be an appropriate candidate for the bipolar plate material due to its gas impermeability and high mechanical strength with respect to graphite as well as formability, low machinery cost and light weight in comparison with titanium and stainless steel. 3,13,18 The main bottleneck of aluminum is corrosion in the working conditions of PEM fuel cells because the presence of an acidic environment (pH ≅ 3) along with fluoride ions (F − ) (washed away from membranes that act as an electrolyte in PEM fuel cells 19 ) and elevated operation temperature (50 to 100 °C) increase the corrosion rate of aluminum. Depositing a protective coating layer on the aluminum substrate has been recommended as a solution.…”

Optimisation of pack chromised stainless steel for proton exchange membrane fuel cells bipolar plates using response surface methodology

“…Bipolar plates are traditionally fabricated from non-porous graphite due to its corrosion resistance and high surface conductivity but its high gas permeability, brittleness and high processing cost are of major concern. Thus, alternative materials such as stainless steel alloys which offer lighter weight, higher mechanical strength and lower production cost advantages over graphite have been considered as potential replacement for graphite [4][5][6][7].…”