**3.1. Electrodeposition**

This is a technique of using electrochemical processes to apply metallic coatings on metals or other conducting surfaces. Electrodeposition is done for the following purposes:


and titanium. This reduces its surface conductivity and rendered it incompetent as bipolar plate material except used in combination with other metals or with suitable coating blend.

Nickel is comparatively inexpensive, and it exhibits good ductility and ease of manufacturing. Pure nickel does not form protective oxide layer like other known bipolar plate materials but is very susceptible to severe corrosion. Therefore, there is need for alloying it with chromium to be very stable at minimum corrosion rate and low electrical resistivity compared to stainless

Copper emerges as the only bipolar plate material with the highest possible electrical and thermal conductivity. Studies have shown that in a stimulated PEMFC environment, copper

Materials such as Al, Cu, Sn, Ni, and Ni-phosphorous are very susceptible to electrochemical corrosion in acidic solutions that are typical of PEMFC operating conditions. However, gold shows very high resistance to electrochemical corrosion, in comparison to graphite, the

In order for its multifunctional roles to be actualized, its material requirement has to be one of excellent electrical and thermal conductivity, good gas permeability, high mechanical strength, high corrosion resistance, and low weight. Having all these required properties locked up in a single material has ever been a challenge facing the research and development community on bipolar plates. As a result, different materials suited for different applications for bipolar plates such as metal, coated metal, graphite, flexible graphite, carbon–carbon composite, and carbon–polymer composites have been adopted over the years. None of these has been able to fulfill at once all the performance requirements and targets set by the US Department of Energy

Techniques here include electrophoretic deposition, electrospray, electrodeposition, and

This is a technique of using electrochemical processes to apply metallic coatings on metals or

**•** Impartation of special surface properties like harness for wear control, toughness for

**•** Protection and barrier intermediary between a material and the environments of influence

other conducting surfaces. Electrodeposition is done for the following purposes:

tribology control, surface roughness for frictional control

beryllium alloy Ce17200 has a corrosion rate of approximately 0.28 μm year at 70°C.

**3. Electrochemical methods of applying coatings on metals**

**2.8. Nickel and their coatings**

246 Electrodeposition of Composite Materials

**2.9. Copper and their coatings**

traditional bipolar plate material.

steel alloys.

for fuel cell.

electroless deposition.

**3.1. Electrodeposition**

Electrodeposition works on the principle of electrolysis. Electroplating utilizes electrolytic cell setup whereby plating metal (anode) and metal to be plated (cathode) are inserted in plating bath containing the solution of a salt of the metal that is to form the coating. The object to be coated is connected to the negative terminal of an electric battery as cathode while the plating metal is connected to the positive terminal of the electric power source as anode. As the electroplating process continues, the metal salts in the bath are used up. If the anode is a bar of the coating metal, the bar dissolves in the bath at the same rate that the bath gives up its metal to the cathode. If the anode is made of another metal, salts of the coating metal must be added to the bath as metal becomes deposited on the cathode. The longer the process continues, the greater the thickness of the coating on the cathode.
