Analysis and countermeasures of corrosion problems of alkaline water electrolysis hydrogen production equipment

1. Adverse effects of corrosion on water electrolysis hydrogen production equipment

The water electrolysis hydrogen production system involves hydrogen, oxygen, potassium hydroxide (or sodium hydroxide) solution and other material media, and various types of corrosion, such as chemical corrosion, electrochemical corrosion, hydrogen embrittlement, alkali embrittlement, etc. If the corrosion problem is not handled properly, it will lead to frequent maintenance and replacement of parts, disrupt the factory production schedule, cause economic losses, and may also cause material leakage, pollute the environment, and endanger personal safety.

1) Performance degradation: Corrosion can lead to a decrease in electrode surface activity, reducing the efficiency of hydrogen and oxygen generation, thereby reducing the overall performance of the electrolyzer.

2) Electrode wear: Over time, corrosion causes the electrode material to wear away, affecting its mechanical strength and conductivity, and may eventually require replacement of the electrode.

3) Uneven gas generation: Uneven electrode surface caused by corrosion may lead to uneven bubble generation, which in turn affects gas separation and collection efficiency.

4) Increased risk of failure: Severe corrosion may cause cracking or failure of electrodes, increasing the risk of failure of the overall electrolyzer system.

5) Increased maintenance costs: Corrosion-induced performance degradation and the need for electrode replacement increase maintenance and operating costs.

2. Corrosion Types and Countermeasures

1) Hydrogen embrittlement: a hidden risk Hydrogen embrittlement is a phenomenon in which the mechanical properties of metals decrease due to hydrogen. It is divided into environmental (external) hydrogen embrittlement, internal hydrogen embrittlement, and reactive hydrogen embrittlement. Among steel materials, carbon steel hydrogen embrittlement increases with the increase of carbon content. Stainless steel also faces the risk of hydrogen embrittlement. Austenitic stainless steel has relatively good resistance to hydrogen embrittlement. Factors such as ambient temperature, hydrogen pressure, strain rate, and processing technology affect the occurrence of hydrogen embrittlement. To prevent hydrogen embrittlement, we can start from reducing hydrogen dissolution, reducing hydrogen concentration, inhibiting hydrogen diffusion, surface treatment, alloying and heat treatment, reducing stress concentration, etc. When selecting materials for the hydrogen production system, we must also carefully consider the compatibility of pipeline and valve materials with hydrogen.

2) Alkali embrittlement: a threat that cannot be underestimated. Alkali embrittlement, also known as stress corrosion cracking, is the brittle cracking of metals under specific corrosive media and tensile stress. Carbon steel is prone to alkali embrittlement in a high concentration of NaOH solution and at a certain temperature. Austenitic chromium-nickel stainless steel also has the risk of alkali embrittlement. The alkali embrittlement range of nickel and nickel-based alloys is relatively narrow. Schematic diagram of stress corrosion. Tianji Hydrogen Energy selects materials for alkaline liquid media. Carbon steel is commonly used for nickel plating of electrolytic cell plates. Pipeline material selection needs to take into account multiple factors. Electrode selection is also particular, such as the common use of nickel-plated soft iron as anode.

3) Electrochemical corrosion: a multifaceted "enemy" Electrochemical corrosion includes stray current corrosion, galvanic corrosion, crevice corrosion, etc. Stray current corrosion originates from the leakage of current in the electrolytic reaction, which will lead to corrosion of the anode metal. It exists in many places, and protective measures include ensuring the insulation of the unit slot, adding sacrificial electrodes, and grounding the main pipe. Galvanic corrosion occurs at the contact point of different metals, and crevice corrosion is related to the environment in the metal crevice.

In addition, there is corrosion at the mastoid apex, plate gas channel, nickel plating and other parts, which require corresponding measures to prevent, such as controlling steam water quality, ensuring that the airway is immersed in alkaline solution, and cleaning impurities in time. At the same time, a variety of corrosion control technologies should be used in combination.

3.Electrolyzer plates: key component considerations

The thickness of nickel plating on the plate of the electrolytic cell should comply with relevant national standards, which is related to the corrosion resistance and conductivity of the plate, and thus affects the performance and life of the electrolytic cell. Salt spray testing is crucial for the plate, which can detect potential corrosion problems in advance, ensure its adaptability and durability in different environments, especially high salt spray environments, meet the industry's requirements for equipment reliability, and adapt to the design needs of new electrolytic cells.

4. Prevention of corrosion in alkaline electrolytic cells

Although alkaline electrolyzers are mature in technology and have low-cost electrode materials, they have a prominent corrosion problem. The cause of corrosion is related to the alkaline environment and the oxygen produced by electrolysis, and the consequences seriously affect the structure and performance. Preventive measures cover material selection and development, electrolyzer design optimization, control logic optimization, surface treatment process optimization and core component matching, and regular maintenance. The corrosion problem of water electrolysis hydrogen production equipment is complex, but by deeply understanding the corrosion mechanism and taking effective protective measures, from material selection, process optimization to daily maintenance, a comprehensive and multi-level protection system can be constructed to ensure the stable operation of the equipment and promote the water electrolysis hydrogen production industry to a more efficient, safe and sustainable development path.