Understanding the Causes of Manhole Cover Corrosion

Manhole cover corrosion is a persistent challenge for public works departments. Corroded covers compromise structural integrity, increase safety risks, and increase maintenance costs. Recognizing what triggers corrosion is essential to effectively combat this issue. This article outlines the primary causes of manhole cover corrosion.

Exposure to Harsh Weather Conditions

Manhole covers often face harsh weather conditions, from freezing winters to hot summers. Professionals using road salts to combat icy conditions speed up the corrosion process. Saltwater seeps into cracks and attacks the metal’s surface, accelerating rust. Regular inspections and waterproof coatings on covers can help reduce this damage, and replacing them with high-quality water-tight cast-iron manhole covers is a good idea, if you can, too.

Chemical Reactions With Sewage and Industrial Waste

Sewage and industrial waste frequently contribute to corrosion in manhole covers. Ammonia, acids, and other chemicals in sewage and industrial discharges react with the metal, accelerating degradation. Using corrosion-resistant materials, such as ductile iron or composite covers, can significantly reduce these reactions.

Microbial Activity and Biogenic Sulfide Corrosion

Bacteria in sewage systems produce hydrogen sulfide gas, which can convert to sulfuric acid. This acid erodes metal covers over time, causing significant damage. Preventing common manhole cover issues involves using protective coatings that minimize the effects of microbial activity and sulfuric acid exposure.

Galvanic Corrosion Due to Dissimilar Metals

Manhole covers sometimes experience galvanic corrosion when two different metals come into contact in a moist environment. The interaction causes one of the metals to corrode faster than it usually would. Consistent material choices and insulating materials between dissimilar metals during installation are vital for preventing this.

Wear and Tear From Heavy Traffic and Machinery

Heavy traffic, construction equipment, and machinery cause immense wear on manhole covers. This sustained weight and friction weaken the covers, making them more susceptible to oxidation and damage. Investing in covers designed to withstand vehicular loads and incorporating regular maintenance can effectively address this issue.

Understanding these causes is key to minimizing manhole cover corrosion. Protective measures such as using appropriate materials, applying advanced coatings, and maintaining proactive regular inspections help keep these challenges in check. Stay ahead of infrastructure concerns by addressing these factors today.