Protection Technology and Application Practice of Manhole Steps in Corrosive Environments

I. Impacts and Hazards of Corrosive Environments on Manhole Steps

Corrosive environments directly damage the structural integrity of manhole steps, shorten their service life, and pose potential safety risks.

Main Corrosion Types and Impacts

· Chemical corrosion: Acid-base solutions and corrosive gases in sewage wells and chemical areas directly erode the step base material, leading to material deterioration and reduced strength.

· Electrochemical corrosion: In underground humid environments, steps create galvanic cells with surrounding metals and soil, which accelerate the rusting and spalling of metal materials like cast iron.

· Physicochemical combined corrosion: Long-term immersion, temperature fluctuations, and the action of corrosive media cause cracks and peeling of the step surface coating, further aggravating base material corrosion.

Core Hazards

· Structural failure: Corrosion thins or fractures steps, making them unable to bear human weight and causing falls.

· Increased maintenance costs: Frequent replacement of corroded steps or anti-corrosion repairs raises engineering operation and maintenance expenses.

· Disruption to project continuity: Corrosion damage to steps may interrupt maintenance operations of underground pipe networks, chemical facilities, etc.

II. Core Protection Technologies for Manhole Steps in Corrosive Environments

For different corrosion intensities and application scenarios, a combined protection scheme of "material selection + surface protection + structural optimization" is required.

1. Material Selection Protection (Root Anti-Corrosion)

· Preferred plastic-steel material: Adopts a structure of high-strength engineering plastic cladding with embedded steel. The plastic layer completely isolates corrosive media, suitable for highly corrosive scenarios such as sewage wells, septic tanks, and chemical areas.

· Upgrade of corrosion-resistant metal materials: Select weathering steel, ductile iron with special alloy components to enhance the corrosion resistance of the metal itself, suitable for moderately corrosive environments.

· Application of aluminum materials: Utilizes the self-protection characteristic of aluminum oxide film, combined with anodizing treatment, ideal for slightly corrosive underground or outdoor scenarios.

2. Surface Protection Technologies (Outer Layer Barrier)

· Coating Protection: Apply hot-dip galvanizing, followed by an epoxy zinc-rich primer and a polyurethane topcoat on cast iron and other metal steps. This process creates a dense protective layer that prevents corrosive substances from contacting the base material.

· Plastic Lining/Coating Treatment: Cover the surface of metal steps with corrosion-resistant plastics, such as polyvinyl chloride (PVC) and polyethylene (PE). This treatment provides both anti-slip and anti-corrosion benefits, making it suitable for humid and corrosive environments.

· Anodic Protection: For metal steps located in large industrial inspection wells, use the sacrificial anode method. This technique protects the base material from corrosion through electrochemical reactions.

3. Structural Design Optimization (Reducing Corrosion Triggers)

· Drainage and anti-slip structure: Design dense anti-slip patterns and drainage grooves on the manhole step surface to avoid accumulation of corrosive media.

· Simplified splicing structure: Reduce welding and bolt connection nodes of steps to prevent local corrosion at gaps.

· Reserved corrosion allowance: Increase a certain thickness of corrosion allowance during the manufacturing of metal steps to extend the actual service life.

III. Selection Principles and Precautions for Protection Technologies

Selection Principles

· Matching corrosion intensity: Prioritize plastic-steel and plastic-lined materials for highly corrosive environments; select coated ductile iron for moderately corrosive environments; choose aluminum or ordinary anti-corrosion metal steps for slightly corrosive environments.

· Balancing cost and service life: Prioritize long-term anti-corrosion schemes for industrial-grade highly corrosive scenarios to reduce long-term maintenance costs; select cost-effective coated metal steps for ordinary municipal scenarios.

· Safety adaptation: For special scenarios such as power and chemical industries, consider both anti-corrosion and insulation, explosion-proof functions to avoid safety hazards caused by single protection.

Precautions

· Ensure the integrity of the protective layer during installation: Avoid scratching the coating and plastic outer layer during transportation and installation; otherwise, local corrosion will occur.

· Regular inspection and maintenance: Conduct annual inspections on the coating integrity of metal protective steps, and check for cracks and peeling of the plastic layer on plastic-steel steps.

· Avoid mixing different materials: Prevent direct contact between different metal steps and surrounding components to avoid electrochemical corrosion.

IV. Conclusion

In corrosive environments, the anti-corrosion protection of manhole steps is a systematic project that integrates material science, structural design, and on-site application. The selection of protection technologies must be based on the actual corrosion intensity, environmental characteristics, and safety requirements of the scenario, to achieve the dual goals of long service life and low maintenance costs.