Rubb Fabric Building News

A recent article in the American Galvanizer’s Association newsletter had some powerful words to share in a comparison of “cold galvanizing” with true hot-dipped galvanization. Dr Galv, the American Galvanizer’s Association resident expert on steel and the galvanization process, strongly rebuked the idea that the application of zinc-rich paint is comparable to hot-dipped galvanization (HDG), the ONLY method that Rubb uses to protect the steel frames of our buildings.

“Cold galvanizing” is really the application of zinc-rich paint (ZRP), and as such the technique is limited to the skill of the painter and the ability to penetrate exposed areas of weld-joints. A complete coat is necessary for there to be any protective benefit, and even so the paint’s corrosion protection is limited by environmental factors and “the amount of zinc dust in the paint, coating thickness, zinc-to-zinc contact, binding material (organic or inorganic), its adhesion to the steel, and completeness of paint coating.” In other words, “your mileage may vary.”

In contrast, hot-dipped galvanization results in a metallurgical reaction between the iron in steel and molten zinc. This results in a permanent coating of layers of zinc-iron alloys and a pure-zinc protective layer. Galvanization results in a consistent coating thickness on all interior and exterior surface. The resulting steel alloy can enjoy a long lifespan with little to no maintenance (After 30+ years, most Rubb structures show no corrosion at all).

Tests reveal a shocking difference in the expected lifespan of metals coated with zinc rich paint vs. hot-dipped galvanization. In every test administered — cathodic protection, salt fog test, 2000 hour immersion test and more — hot-dipped galvanized metal significantly outperformed ZRP steel. In most cases, hot-dipped galavanized steel showed no corrosion while ZRP steel was significantly damaged!

In the real-world, this can translate into a variety of problems for building owners with products that have been cold galvanized rather than hot-dipped galvanized. For example, because zinc-rich paint can only be applied to the exterior of a surface, a steel frame may appear to be intact while it is slowly rotting from the inside! This kind of damage is nearly undetectable until it is too late to prevent it. In contrast, HDG steel is thoroughly protected inside and out to a significantly higher degree than ZRP steel.

When evaluating steel-framed products, keep a close eye on the quality of the construction. While zinc-rich paint products are often initially less expensive than hot-dipped galvanized products, the cost of inferior engineering over the life-span of a structure more than makes up for the difference. From the beginning, Rubb has been dedicated to producing products of the highest caliber, and post-production hot-dipped galvanized is just one way we add lasting value and integrity to our structures.