How Long Does It Take Zinc Coating on Rebar to Corrode?

How long does it take zinc coating on rebar to corrode?

There are several factors that influence the longevity of the zinc coating and some testing methods have not told the complete story. The question is complex, and requires a more detailed explanation.

Therefore, we’ll delve into more information to provide the answers to this multifaceted question and discuss why zinc remains the ideal choice to protect your project.

At South Atlantic, you can trust in the longevity of our galvanized rebar. The zinc coating protects it from corrosion, even in hostile environments, which is why it’s such a popular choice with bridges and other DOT projects. See why national companies have trusted us for more than 50 years, because at South Atlantic, we’ve got you covered. Simply contact us for a quote.

How Long Does It Take Zinc Coating on Rebar to Corrode? 

Galvanized coating is unlike any other coating because it initially acts as a barrier. What happens is that the coating slowly degrades and then reseals itself. When things start to depassivate, the surface is no longer passive, and on steel, that’s when you begin to see rust. 

But the unique aspect of zinc is that it will depassivate and corrode slightly, then repassivate and go back to neutral, maintaining its strength. This does not occur in steel and other metals. Many researchers and testing methods do not take that into account. So how long does it take zinc coating on rebar to corrode? requires a more detailed answer.

Zinc Protection Can Outlive the Projects

Perhaps the best measurement of how long it takes zinc coating on rebar to corrode lies within data for bridges constructed in the 60s or 70s. When a hole is drilled to examine the rebar, there is still a more than adequate zinc coating to continually provide the most robust protection in hostile environments. 

Another challenge in measuring the corrosion-resistance of galvanized rebar is that there weren’t any original measurements taken of the zinc layer when many of these were originally constructed. 

The question then becomes how many millimeters of coating do you need to give you the service life you’re looking for? It’s not unusual for zinc coatings to outlive the project itself, so many organizations will find it more economical to only get the minimal amount of coating needed. This is another facet that has to be considered when examining the corrosion rate.

Some rebar, like 767 rebar and  1094 rebar, can give you well over 100 years of life—which will outlast many projects.

In fact, the International Zinc Association states that a 5 mm coating can last as long as 300 years. This is very different from the 10 to 12 years cited by those doing accelerated testing. 

Evidence of the Longevity of Zinc Coating

When examining bridges and other structures that have damage, it was discovered that the zinc coating on the rebar remained intact—so in many cases, the zinc coating will outlast the structure. 

For evidence, we present the Longbird Bermuda Bridge Project. Built in 1953, the bridge survived a harsh marine environment, and after 42 years of heavy traffic, the bridge’s zinc coating retained its thickness. (You can read more about this project in our earlier blog.)

This is much longer than many spray tests would report.

How Much Zinc Coating Is Sufficient?

Different types of rebar have different levels of coating, but the question centers around how much coating is necessary to give the service life you need. In certain cases, if the rebar gives you more than 100 years of protection, and if the life of the overall structure is expected to be 50 years, the zinc coating will last longer than the project is designed. 

Zinc: The Undisputed Leader in Safeguarding Your Projects

When the interstate highway system was built, there was a huge problem: Everywhere roads were salted, a lot of new bridges were failing. Galvanized rebar is the solution.

Did you know that $400 billion could be saved simply by utilizing corrosion control methods like galvanizing? In fact, the International Zinc Association states that zinc is so vital to this role that the coating market represents 60% of total zinc consumption annually. 

South Atlantic Has You Covered to Help Your Projects Stand the Test of Time

We provide more than products and services. We provide peace of mind knowing that your project is built to last. And you won’t have to worry about delivery. We’re ready to ship to all 50 states. With a stringent QA process, our reliability means you can count on your delivery dates. Be sure to ask us about our proprietary air-wiping and how it can benefit your product. It’s just another way that we have you covered.

Ready to get started? Request a quote today.