How does surface passivation treatment of stainless steel electrolytic tubes enhance their resistance to oxidation and scaling?
Publish Time: 2025-08-14
In industrial applications, stainless steel electrolytic tubes are widely used in critical scenarios such as water electrolysis for hydrogen production, electrochemical processing, cooling systems, and high-temperature fluid transmission. Their long-term operational stability and efficiency are highly dependent on the chemical stability and cleanliness of the tube surface. Surface passivation can significantly improve the oxidation and scaling resistance of stainless steel electrolytic tubes under complex operating conditions, extending their service life and reducing maintenance costs.Optimizing Surface MicrostructurePassivation treatment chemically or electrochemically removes free iron, machining residues, and microburrs from the stainless steel surface, making the previously rough or defective surface denser and smoother. This optimized microstructure reduces the number of surface active sites, lowering the probability of oxidation reactions between the metal and the surrounding media (such as water, oxygen, and electrolyte). In the electrolytic environment, a smooth surface is less likely to form localized micro-cell effects, effectively inhibiting metal dissolution in the anodic region and slowing the progression of oxidative corrosion. At the same time, the passivated surface forms a uniform, continuous, chromium-rich layer. Although extremely thin (typically only a few nanometers), this layer is densely structured and chemically inert, effectively blocking the penetration of corrosive ions (such as chloride and sulfate) into the metal matrix, further enhancing its antioxidant properties.Physical and Chemical Mechanisms of Scaling InhibitionDuring electrolysis or heat exchange processes, calcium, magnesium, and silicon ions in water easily deposit on metal surfaces, forming scale, which severely impacts heat transfer efficiency and current distribution. Passivation treatment modifies the surface energy and charge characteristics of stainless steel, reducing its tendency to adsorb mineral ions. The treated surface exhibits lower surface free energy, making it more likely that water molecules will form a loose hydration layer, hindering the direct attachment of scale-forming ions. Furthermore, the chromium oxide in the passivation layer exhibits strong hydrophilicity and anti-adhesion properties, reducing the adhesion of scale particles. Even if small deposits do form, they are easily removed by fluid flushing or regular cleaning, preventing the formation of stubborn scale deposits. This characteristic is particularly important in continuously operating electrolysis systems, significantly extending cleaning cycles and maintaining stable electrolysis efficiency.Improving Chloride Ion Corrosion ResistanceIn chloride-containing environments (such as seawater electrolysis or industrial cooling water systems), chloride ions easily penetrate the oxide film on stainless steel surfaces, causing pitting and crevice corrosion. Passivation treatment significantly improves the material's resistance to chloride ions by strengthening the density and integrity of the oxide film. The optimized passivation process forms a thicker, more stable passive film with a higher chromium/iron ratio and enhanced self-healing properties. Even after localized damage, it can quickly regenerate in an oxygen-rich environment, preventing further corrosion. This enhanced chloride corrosion resistance directly improves the long-term stability of electrolysis tubes in high-salinity environments, preventing equipment failure caused by pitting and perforation.Delaying High-Temperature Oxidation and Thermal FatigueUnder high-temperature electrolysis or thermal cycling conditions, stainless steel surfaces are prone to oxidation thickening and scale flaking, leading to material loss and performance degradation. The stable oxide layer preformed during passivation serves as a "sacrificial layer," slowing the continuous oxidation rate of the base metal at high temperatures. This layer exhibits excellent thermal stability, resists cracking or flaking, and effectively protects the underlying metal. Furthermore, the well-matched thermal expansion coefficients between the passivation layer and the base metal reduce microcracks caused by thermal stress and enhance the material's durability during thermal cycling. This is particularly important for electrolytic systems subject to frequent starts and stops or variable operating conditions.Enhanced Compatibility with the Electrolytic EnvironmentPassivated stainless steel electrolytic tubes exhibit lower background current and higher electrochemical stability in the electrolyte. The removal of surface impurities and the uniformity of the oxide film reduce unwanted side reactions and localized current concentration, helping to maintain uniform and efficient electrolysis. Furthermore, the passivation layer acts as a selective barrier to the migration of hydroxide and metal ions, reducing byproduct deposition on the electrode surface and indirectly inhibiting scale formation.Long-term economical operation and maintenance advantagesDue to improved resistance to oxidation and scaling, passivated stainless steel electrolytic tubes exhibit longer maintenance cycles and higher reliability in actual operation. This reduces downtime for cleaning and fitting replacement, reducing operating costs. Furthermore, the stability of the overall system efficiency improves energy efficiency, aligning with green manufacturing and sustainable development requirements.Surface passivation treatment of stainless steel electrolytic tubes significantly enhances their resistance to oxidation and scaling under complex operating conditions by optimizing the surface microstructure, enhancing oxide film stability, and reducing surface activity and adsorption. This not only extends the equipment's service life but also ensures efficient and stable operation of the electrolysis process, making it a key process step in improving the overall performance of industrial electrolysis systems.
