Corrosion Behavior of Passivated 316LSS with Ag Coating as PEMFC Bipolar Plate

Abstract

A new chemical passivation technique, which contained 20 g/L hydrogen peroxide, 3.75 g/L sodium silicate, 1.25 g/L sodium carbonate, 3.75 g/L lactic acid and 0.75 g/L 8-hydroxyquinoline, was used to modify 316 stainless steel with Ag coating (Ag-coated 316SS) as PEMFC bipolar plates. The results indicated that the compact passive film had been obtained on the surface of Agcoated 316SS. The passivation process could not only increase contact angle (from 58• to 104 • ) but also decreased pinhole defects of Ag-coated 316SS. Electrochemical test manifested that the passivation process could reduce Ag-coated 316SS's double layer capacitance (C d ), and increase its charge transfer resistance. So, it provided significant protection against corrosion for Ag-coated 316SS in PEMFC environment.

Metallic Material Selection and Prospective Surface Treatments for Proton Exchange Membrane Fuel Cell Bipolar Plates—A Review

“…Capacitance and resistance properties related to layer thickness and resistance are monitored-the existence of defects, such as pores or cracks, means easier penetration of electrolyte through the coating or passive layer, which results in a decrease in the number of protective layers [10]. The most frequently selected parameters correspond to the frequency range of 100 kHz to 10 mHz at free corrosion potential with an amplitude of 5-10 mV [30][31][32][33]. Another possibility is to use the same frequency for measurements at potentials corresponding to fuel cell conditions, −0.1 V and +0.6 V vs. SCE [34,35].…”

“…In addition to the already mentioned nitrides, carbides, carbon, and polymer coating, there are other coatings which are studied metals (Au, Ag, Ni, Ta, Nb, and Zr) [33,38,87,137], oxides (e.g., SnO 2 and PbO 2 ) [138][139][140][141], or various combinations, such as Ni-P, Ni-Mo [39]. Ni-Mo and Ni-Mo-P coatings prepared on 304 steel by electrodeposition form a more compact layer with the addition of phosphorus.…”

“…The corrosion properties were improved, but localized corrosion due to the presence of pores can be a problem. Defects in the structure of the coating are also a problem for silver coatings; therefore, chemical passivation in chromate-free solution to improve the properties of the 316L steel coated with silver has been attempted [33]. A smoother coating was achieved with fewer defects and hydrophobicity, and the corrosion properties improved, but the corrosion current density was still well above the DOE limit.…”

Corrosion behavior of tantalum coatings on AISI 316L stainless steel substrate for bipolar plates of PEM fuel cells

“…To minimize the effects of metallic corrosion without reducing the electrical conductivity, different surface modification techniques have been proposed together with corrosionresistant coatings [14], [15], [16], [17]. Different coatings have been tested, some of them based on noble metals [18], [19], metal carbides and nitrides [20], [21], [22], [23], as well as 4…”