1.Can ordinary cold-rolled carbon steel coils (such as SPCC) be directly used as electrode plates for hydrogen fuel cells?
Ordinary cold-rolled carbon steel (low-carbon steel) is unacceptable because it corrodes rapidly in the harsh, acidic, humid, and electrically charged environment of fuel cells, leading to performance degradation and contamination, and is therefore rejected outright.
Cold-rolled stainless steel coils are an excellent candidate substrate: Through precision cold rolling to achieve the required thinness and dimensional accuracy, followed by advanced surface modification coatings, it can meet almost all the requirements of metal bipolar plates, representing a crucial direction for current commercialization.
2.What are the extreme requirements for bipolar plates in hydrogen fuel cells?
High corrosion resistance: Operating environment: ~80°C, humid, acidic (pH 2-3), with electrode potential. Materials must be long-term stable with extremely low corrosion rates.
High conductivity: Surface contact resistance must be extremely low to reduce internal cell resistance and improve efficiency.
Excellent hermeticity: Absolutely prevents hydrogen and oxygen cross-contamination.
Good mechanical strength and formability: Electrode thickness is typically only 0.05-0.2 mm, requiring support for the entire fuel cell stack pressure and the ability to precisely imprint complex flow channels onto it.
Low density and low cost: Facilitates increased power density and commercialization.
3.Why was ordinary cold-rolled carbon steel phased out?
Corrosion resistance: Completely unacceptable. Rapid generalized corrosion and pitting will occur in the fuel cell environment, leading to:
Metal ion leaching, poisoning the catalyst.
Increased contact resistance due to corrosion products.
Inferior airtightness due to substrate corrosion.
Surface conductivity: Poor. The naturally formed oxide layer on the carbon steel surface is non-conductive, resulting in high contact resistance.
Weight: Heavy. High density, which is detrimental to increasing power density.
4.Why have cold-rolled stainless steel coils become the mainstream metal substrate?
Inherent Advantages:
Excellent corrosion resistance: Several orders of magnitude higher than carbon steel.
High strength and toughness: Suitable for ultra-thinning (cold-rolled to 0.05mm) and precision stamping.
Inherently excellent airtightness.
Perfect sheet shape and dimensional accuracy can be achieved through cold rolling.
Acquired Bottlenecks and Solutions: The "passivation film" (chromium oxide) of stainless steel is still not stable enough in the fuel cell environment, and its contact resistance remains high. Therefore, a functionalized coating must be applied to its surface, which is the core technology.
Coating Goal: To provide both "conductive armor" and "corrosion protection barrier" functions.
Mainstream Coating Technologies:
Physical Vapor Deposition (PVD): Such as gold plating, platinum plating (excellent performance but expensive), or more mainstream carbon-based coatings (such as diamond-like carbon (DLC), graphite carbon).
Chemical Vapor Deposition (CVD).
5.What is the role and process chain of cold-rolled coil in this industry chain?
A typical production process for a cold-rolled stainless steel bipolar sheet is as follows: Stainless steel smelting → Hot rolling → Pickling → Cold rolling (to the target thinnest specification, such as 0.1mm) → Annealing → Finishing → Precision slitting → Precision stamping (forming runners) → Cleaning → Surface coating treatment (PVD/CVD, etc.) → Inspection and packaging
The key role of the cold rolling stage: Providing substrate strip coils with uniform thickness, straight shape, smooth surface, and consistent mechanical properties. Its quality directly determines the yield of subsequent stamping and the uniformity of the coating.