Protecting Screw Piles from Corrosion

Screw piles are a popular foundation material. They are highly durable and capable of withstanding significant loads. However, like any metallic material, they are susceptible to damage. Protecting screw piles from corrosion is an important aspect that affects the service life of a screw pile foundation. In this article, we will discuss the causes of screw pile failure, types of corrosion, and methods of corrosion protection.

Causes of Screw Pile Failure

• Humidity. A humid environment accelerates the oxidation of metal surfaces.

• Salt solutions. Soil containing salts destroys protective layers.

• Soil acidity. Acidic soil accelerates rusting.

• Stray currents. Electrical fields in the soil can cause electrochemical corrosion.

• Mechanical damage. Piles can be damaged during installation or operation, compromising the protective layer and exposing the metal.

• Chemical reactivity of the soil. Alkaline and acidic environments have a strong effect on metal.

• Lack of treatment. Supports without an anti-corrosion layer rust more quickly.

Types of corrosion

• Electrochemical: Occurs when metal comes into contact with an electrolyte, such as moist soil. This process is accompanied by the formation of a galvanic pair, where one metal acts as the anode (destroyed) and the other as the cathode (remains intact). To protect against electrochemical corrosion, it is recommended to use insulating coatings and galvanized piles.

• Chemical: Occurs as a result of direct contact between metal and aggressive substances. Soil may contain acids, alkalis, chlorides, and sulfates, which react with the pile surface. Deformations from chemical corrosion manifest themselves as pitting or generalized erosion of the metal surface. To minimize the risk of chemical corrosion, anti-corrosion compounds are used to create a barrier between the metal and the aggressive environment.

• Mechanical erosion: Occurs due to friction between soil particles and the pile surface, especially during screw installation or in unstable soil conditions. This damages the protective layer, accelerating rusting of the screw pile walls. To combat this type of corrosion, it is necessary to use durable coatings such as polyurethane and epoxy.

How to avoid corrosion of screw piles?

• Selecting piles. Purchase piles with a factory-applied anti-corrosion coating.

• Protection from mechanical damage: During installation and operation, avoid mechanical damage to the metal.

• Careful preparation. After installation, piles are treated with paint or protective compounds.

• Considering the soil type. For aggressive soils, choose piles with enhanced protection.

• Regular inspection. An annual foundation inspection will allow for timely repair of damage.

• Galvanizing. Galvanized piles are corrosion-resistant and have a long service life.

• Installation. Installation must be carried out in compliance with all technical requirements.

By following these recommendations, you will extend the service life of the foundation.

Anti-corrosion Protection Methods

Anti-corrosion protection of piles helps prevent their destruction. Let's look at the main methods.

1. Polymer Coatings

These are layers of materials resistant to corrosion and mechanical damage. They create a durable, waterproof layer on the metal surface, preventing contact with aggressive environments.

Advantages:

• Excellent adhesion.

• Moisture and chemical resistance.

• Durability.

Popular types of polymer coatings are epoxy and polyurethane compounds.

2. Epoxy

This is a two-component coating with chemical resistance and good adhesion to metal. The epoxy coating creates a dense layer, preventing contact of the metal with moisture and aggressive substances.

Advantages:

• High strength.

• Chemical resistance.

• Easy to apply.

3. Polyurethane

The elastic polyurethane coating is resistant to UV radiation. Suitable for protecting screw piles in various climatic conditions, including areas with unstable soils.

Features:

• Resistance to mechanical damage.

• Durability (up to 30 years).

• Can be applied in multiple layers for enhanced adhesion.

4. Galvanizing

The process of applying a zinc layer to a metal surface for corrosion protection. Zinc, being a more reactive metal than steel, absorbs the effects of aggressive environments, protecting the steel from deterioration. There are two galvanizing methods: hot-dip galvanizing and cold galvanizing.

Hot-dip galvanizing

Hot-dip galvanizing involves immersing the metal element in molten zinc. This method provides a dense coating that is resistant to aggressive environments.

Advantages:

• High reliability.

• Long service life (up to 50 years).

Cold Galvanizing

Cold galvanizing is the application of a zinc-containing compound to the metal surface using a spray method.

Advantages of this method:

• Ease of application.

• Can be used after pile installation.

• Good waterproofing.