What are the best corrosion-resistant materials for deep foundation design?

1 Types of corrosion

Corrosion is a deterioration of a material due to a chemical or electrochemical reaction with its environment. Different types of corrosion can affect deep foundations, depending on the material, the soil, and the exposure conditions. Uniform corrosion is the most common and predictable type, where the material loses mass evenly over its surface. Pitting corrosion is a localized type, where small holes or pits form on the surface due to chloride ions or microbiological activity. Crevice corrosion is another localized type, which occurs when narrow gaps or crevices trap stagnant water or soil and create a corrosive environment. Galvanic corrosion is when two dissimilar metals are in contact and form a galvanic cell, where one metal acts as an anode and corrodes faster than the other. Finally, stress corrosion cracking occurs when a material is subjected to tensile stress and a corrosive environment, causing cracks to initiate and propagate.

2 Corrosion-resistant materials

Deep foundation design requires corrosion-resistant materials that can withstand the corrosive effects of the soil and environment, while still providing adequate strength, stiffness, and durability. Steel is a strong and versatile material that can be shaped into various forms of deep foundations, but it can be prone to corrosion. To protect steel from corrosion, coatings, cathodic protection, or sacrificial anodes can be applied, or stainless steel or weathering steel alloys can be used. Concrete is a durable and economical material for deep foundations, but it can suffer from corrosion when the reinforcing steel bars inside it are exposed to chloride ions, carbonation, or sulphates. High-quality concrete with low permeability and adequate cover depth can help prevent concrete corrosion, as well as corrosion inhibitors, epoxy-coated rebars, or fibre-reinforced polymers. Timber is a natural and renewable material for deep foundations that has a high strength-to-weight ratio but low resistance to fire and decay. It can also be affected by corrosion when exposed to fungal or bacterial attacks, or marine borers. To protect timber from corrosion, preservatives, paints, plastic wrappings, treated wood species are some of the options available.

4 Corrosion mitigation strategies

Civil engineers need to implement corrosion mitigation strategies to reduce the impact of corrosion on deep foundation design, and enhance the protection, performance, and service life of the material. Material selection is essential for choosing the most suitable material based on its corrosion resistance, strength, stiffness, durability, and cost. Design optimization should be done to minimize exposure to corrosive agents and reduce stress concentration. Corrosion control involves applying various methods or techniques to prevent or slow down the corrosion process, such as coatings, cathodic protection, sacrificial anodes, corrosion inhibitors, or electrochemical treatments. Additionally, standards and codes of practice should be followed to ensure minimum requirements and guidelines for deep foundation design are met. Finally, it's important to monitor and evaluate the effectiveness and durability of the corrosion control methods.