Stainless Steel Separator Coating for Fuel Cell Corrosion
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Solution Overview
Problem
Proton-exchange membrane fuel cells face challenges with corrosion resistance in wide potential ranges due to transpassive dissolution of chromium in stainless steel separators, especially at high potentials, limiting their durability and increasing costs.
Innovation Solution
Enhancing oxidic bonds in a surface coating and controlling the Cr-to-Fe ratio through anodic electrolyzation of stainless steel with 16% or more Cr in an electrolyte solution containing sodium sulfate, forming a coating with an intensity ratio of (OO/OH)/(Cr/Fe) of 1.0 or more, improves corrosion resistance across a wide potential range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If stainless steel is used as separator material to replace carbon materials, then cost is reduced and mechanical strength is improved, but corrosion resistance in wide potential range deteriorates due to transpassive dissolution of Cr
Solution Approach 1:
The patent applies preliminary action by performing anodic electrolyzation treatment before the fuel cell operates. This treatment pre-forms a protective oxide coating on the stainless steel separator surface, enhancing corrosion resistance in advance. The coating is formed by oxidizing the steel surface in an electrolyte solution containing sulfate ions, creating a stable passive layer that prevents transpassive dissolution during subsequent fuel cell operation.
Solution Approach 2:
The patent changes physical and chemical parameters of the stainless steel surface through controlled anodic electrolyzation. By adjusting parameters such as electrolyte composition (sulfate concentration), applied potential, temperature, and treatment time, the oxide coating composition is optimized to achieve high corrosion resistance. The Cr-to-Fe ratio in the oxide layer is specifically controlled to prevent chromium dissolution while maintaining passivity across wide potential ranges.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides stainless steel separators with enhanced corrosion resistance in fuel cell environments, reducing costs and extending durability, making them suitable for long-term use in fuel cells.
Implementation Method 1
controlling the Cr-to-Fe ratio in an adequate range through performing anodic electrolyzation of a stainless steel having 16% by mass or more Cr
Implementation Method 2
enhancing oxidic bonds in a surface coating
Data Source
Figure 1
AI summary
A stainless steel for a fuel cell having good corrosion resistance throughout a wide potential range and a method for producing the same are provided. In particular, a coating having an intensity ratio [(OO/OH)/(Cr/Fe)] of 1.0 or more determined by X-ray photoelectron spectroscopy analysis is formed by performing an anodic electrolyzation treatment on a surface of a stainless steel in an electrolyte solution, the stainless steel containing 16% by mass or more of Cr and preferably having a composition that includes, in terms of percent by mass, C: 0.03% or less, Si: 1.0% or less, Mn: 1.0% or less, S: 0.01% or less, P: 0.05% or less, Al: 0.20% or less, N: 0.03% or less, Cr: 20 to 40%, at least one selected from Nb, Ti, and Zr, in total: 1.0% or less, and the balance being Fe and unavoidable impurities.