Brass globe valves are widely used in civil water supply and drainage, HVAC systems, and light industrial pipelines for their excellent thermal conductivity, formability, and cost-effectiveness. However, they are prone to pitting and dezincification in corrosive media or harsh environments, which affects their sealing performance and service life. Thus, a three-in-one corrosion-resistant system integrating base material modification, surface protection, and structural optimization has been developed.

I. Base Material Modification: Enhancing Intrinsic Corrosion Resistance

To enhance the inherent corrosion resistance of brass globe valves, it is essential to modify the base material. This involves optimizing the alloy composition and refining the casting processes. Adding trace elements such as arsenic, tin, and aluminum to copper-zinc alloys helps inhibit dezincification. Specifically, arsenic creates a dense oxide film that prevents zinc from leaching, while tin enhances strength and improves resistance to acid and alkali. Naval brass and tin brass are commonly used materials, with dezincification rates kept to a maximum depth of 0.01 mm per year. Additionally, using low-pressure casting instead of traditional sand casting reduces internal defects like blowholes, which helps avert localized corrosion. Finally, post-casting annealing at temperatures between 300°C and 400°C for 2 to 3 hours is crucial for relieving casting stress and decreasing the risks of stress corrosion cracking.

II. Surface Protection: Forming a Corrosion-Resistant Barrier

This widely used method isolates corrosive media from brass, effectively protecting brass globe valves via physical or chemical coatings. Electroplating options include nickel plating, which withstands over 480 hours of neutral salt spray, suitable for coastal/humid outdoor environments, and cost-effective zinc plating with chromate passivation. Spray coating processes encompass epoxy resin spraying, offering acid-alkali and organic solvent resistance for mild chemical pipelines and PTFE coating, enhancing sealing, suitable for the food/pharmaceutical industries with strict purity requirements. Eco-friendly silane treatment replaces chromate passivation, forming a conversion film that resists over 200 hours of salt spray and meets RoHS standards.​

III. Structural Optimization: Reducing Corrosion Vulnerabilities

Structural improvements for brass globe valves minimize medium stagnation and turbulence. The inner cavity is streamlined to eliminate dead zones, and valve seats/discs are mirror-polished to reduce corrosion attachment sites. A bottom drain hole empties residual medium when idle, and a top vent valve prevents oxygen corrosion, ideal for HVAC systems with alternating temperatures. Corrosion-resistant FKM and EPDM sealing rings replace traditional rubber ones, enhancing temperature/corrosion resistance and avoiding galvanic corrosion between seals and brass.

IV. Application and Selection Recommendations

Different corrosion-resistant processes are suited to different application scenarios: zinc plating with passivation is sufficient for dry indoor environments; nickel plating or epoxy resin spraying is preferred for coastal areas with high salt spray; PTFE coating or naval brass base material is recommended for chemical fluid pipelines. In practical applications, it is necessary to combine base material modification and surface protection processes based on parameters such as medium composition, temperature, and pressure, to achieve the optimal balance between corrosion resistance and cost.