Corrosion is a major problem with structural steel, even in relatively dry environments. Steel rusts very quickly compared to other metals because of the way that it interacts with oxygen in the air. When steel oxidizes, the iron oxide that's formed immediately spalls and flakes away, exposing more steel to the air. Rust can quickly spread through steel structures, compromising their strength and integrity.
In order to combat this, many steel producers coat their steel products with zinc in order to produce galvanized steel. Zinc has a much greater electronegativity than steel, which means that oxygen in the air will react with it preferentially. The steel underneath will be spared. Unfortunately, galvanization doesn't permanently protect a steel structure from rust. Read on to find out why you still need to apply a corrosion-resistant industrial coating to the steel for maximum protection.
The Zinc Coating Thins Over Time
The major downside of relying solely on the zinc coating to protect the steel underneath from corrosion is that the zinc eventually wears away. The zinc turns into zinc oxide as it corrodes, causing the zinc layer to become thinner. Once enough of the zinc has oxidized, the steel underneath will be exposed to oxygen and will quickly rust.
Thankfully, this process is extremely slow. However, re-coating steel structures in the field can be expensive (or even impossible, if the structure is submerged in water or buried underground). In order to best protect your steel structures, you'll need to combine the zinc with an industrial coating.
Industrial Coatings Slow Down the Zinc Degradation
Corrosion-resistant industrial coatings don't directly inhibit corrosion on their own. However, they still help protect the steel underneath. Anti-corrosion coatings act as a barrier that keeps air and water away from the zinc layer on the steel structure. When less oxygen is allowed to chemically react with the zinc, the rate at which it oxidizes is slowed down drastically. Your steel structure will be protected from rust for a much longer period of time as a result.
Zinc Can Be Re-Added With Industrial Painting
In addition, zinc-rich primer can also be used as part of the industrial painting process to provide even more protection to steel structures. These primers contain a considerable amount of dissolved zinc, which further protects the steel underneath. Similar to the zinc layer on the steel, the zinc in the primer will react with oxygen to form zinc oxide before it's able to rust the steel.
To provide your steel structures with the greatest amount of protection, contact an industrial coating contractor in your area and ask about corrosion-resistant coating and zinc-rich primer. By combining the two, you'll greatly extend the lifespan of the protective zinc layer and enhance its ability to protect the underlying steel from rust.
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