"How long can a helical pile foundation last for?"
That's a question the team at VersaPile often hears from the estimators and engineers who are assessing a helical foundation solution. It's a great question, who wouldn't want to make sure they're investing in a durable and long-term foundation?
Even though it's a great question, you might be surprised to learn that it doesn't quite have a straightforward answer.
While it might not have a straightforward answer, however, an answer to the question does exist.
Join us in this post and learn:
● Which key factors affect the lifespan of a helical pile foundation● What techniques designers can use to increase the lifespan of a helical pile● How long could a helical pile last in a Canadian climate?

These Key Soil Factors Affect The Lifespan of a Helical Pile

There's a number of key factors that influence how long a helical pile can maintain its structural integrity after installation. When it comes to steel components installed into the ground, a common concern among engineers and planners is corrosion.
The soil your project is going to be built on contains an uncountable number of components, chemicals, and microorganisms. Each of those "soil factors" are influenced by the type of soil, temperature, moisture content, ground pollution, physical properties, and more. Together, they create the soil conditions you'll contend with at your building site.

Corrosion (in the form of rust) is an ever-present threat to materials like steel and would likely be one of the chief causes of the eventual failure of a helical pile

Let's pretend you install two identical helical piles, but at different locations that have unique soil conditions. If you could fast-forward a few decades and uninstall the piles, odds are good the two piles will have different levels of corrosion. This is because the soil compositions at the two installation sites degrade the piles at different rates.
All this being said, there's something important to note:
One of the necessary components needed for steel to corrode is oxygen, as it's the process of oxidization that converts iron in the steel to iron oxide (rust). Oxygen is present in our soil, but only in disturbed layers relatively close to the surface. Once you get down into undisturbed layers the oxygen levels drop to a point where the environment doesn't support significant corrosion.
Because helical piles do not cause major disturbance to the soil like excavation can, the majority of the pile will end up sitting in undisturbed soils with low oxygen. The result is that, for most of the helical pile, corrosion of the steel won't be a concern to the structural integrity.
Corrosion of the helical pile will be a bigger concern in the upper few feet of soil and above the ground, where oxygen is plentiful to facilitate oxidization of the steel. So, when we're talking about the lifespan of a helical pile foundation, we're really considering how the upper few feet of the pile will perform.
With that out of the way let's uncover which factors cause helical pile corrosion, how engineers can defend against it, and how long a helical pile might last in the ground. We'll start by examining what exactly contributes to the corrosive potential of a soil.

Protecting Helical Pile Foundations From Soil Corrosion

Now that we've looked at some of the factors that contribute to the rate of steel corrosion, it's time to talk about what a helical pile designer or engineer can do to overcome it.
Humans have been putting steel and other metals into the ground for hundreds of years. As a result, huge amounts of research and experimentation has gone into understanding how quickly steel corrodes and what factors affect that corrosion.
Helical pile manufacturers and contractors use this established information to mitigate corrosion, ensuring the foundations will meet and even exceed their expected service life, including a safety margin. The specific tactics used to shield against corrosion are influenced by factors like on-site conditions, environmental considerations, and load requirements.
As always, it's important to have a keen understanding of what's happening in the soil at your jobsite before you make final decisions about your foundation. A quality geotechnical report can reveal unexpected soil conditions that could result in delays and budget overruns.
Let's assume, then, that you have a geotechnical report indicating your soil is more corrosive than normal. What can your helical pile contractor do to ensure your foundation performs as expected for the entire duration of its' service life?

Sacrificial Steel Thickness

One cost-effective and straightforward way to deal with corrosive soil is to simply increase the thickness of the steel on the helical pile. By adding more material to the helical pile shaft, helix plate, and other components, it will take longer for the structural integrity of the steel to be threatened by corrosion.
While it's true that adding more material to the helical piles may moderately increase their cost, it can prolong the lifespan of a helical pile in especially corrosive soils and ensure reliable performance in the long run.
Benefits of Sacrificial Steel Thickness● Easy and cost-effective● Durable and long-lasting protection● No coating that can be damaged or scratched● Requires no special facilities for applying coating

The more material on a helical pile, the more it will have to corrode before the structural integrity is threatened

Galvanization / Epoxy Coatings

Galvanizing helical piles is a common practice in the industry and adds strong protection against corrosion. Other coatings such as coal tar epoxy may be used instead of galvanization, but the idea is the same. These types of protective coatings increase the cost of each helical pile, but the benefit is added corrosion protection (especially for saturated soils or marine environments).
Your helical contractor should tell you if they recommend a coating to be applied to your piles and why the recommend it. Sometimes sacrificial thickness can be used to improve pile lifespan in corrosive environments, which avoids the time and cost of applying a coating
Benefits of Galvanization / Coatings● Can provide excellent long-term protection● Suitable for harsh marine or wetland environments● Galvanization protects pile even if scratched/damaged● Epoxy coating is non-conductive

These helical piles have been given a galvanized coating to greatly increase their resistance to corrosion

Sacrificial Anodes

Sacrificial anodes are reactive metals used to protect less reactive surfaces, like steel, from rusting. They're made from metal alloys more prone to rusting than the helical pile they protect. The difference in "rusting potential" between the sacrificial anode and helical pile causes the anode to rust while the pile stays protected. Hence the name "sacrificial anode".
These are a popular form of active corrosion protection on a helical pile and can be highly effective when used correctly and in the appropriate scenarios.
Benefits of Sacrificial Anodes● Active protection without need for external power● Effective when used correctly● Easy and straightforward to install● Inspection and maintenance is simple

This is one configuration a sacrificial anode may be installed in, others might attach directly to the shaft of the helical pile like a collar