Zinc stops rust. It's as simple as that. And, hot-dipped galvanizing is one of the best ways to apply zinc to metals such as iron and steel, says Joe Langemeier, Southern Operations marketing manager for AZZ Galvanizing Services, Ft. Worth, Tex.
Langemeier, whose roots go back to farming, ranching and the irrigation business in Nebraska, says his goal is to increase awareness of the benefits of galvanizing to farm and ranch operators whose equipment operates in some of the most corrosive environments in American industry.
"I drive across the country and see trailers, gates, cattle panels and a host of other equipment rusting, and think 'All that could be prevented,' " he says. "While he's first to admit farmers and ranchers don't write the specifications on equipment they buy, they do have influence on dealers and manufactures in buying those products that last."
Langemeier recalls a popular promotional item done by an irrigation manufacturing company several years back that featured a photo of one of the first center pivot irrigation rigs ever built. The advertisement read, "Why do we show you a 40-year-old irrigation rig? Because we can!" That, he says, is why galvanizing should be important to farmers and ranchers.
Langemeier says up-front costs of using hot-dipped galvanizing to protect metal, instead of paint, will be similar, but when you consider the overall cost of ownership and maintenance, galvanizing beats paint significantly, particularly if painted material has to be repainted. "Galvanized steel will last 60-70 years without maintenance, you know how long paint lasts," he adds.
How it works
Galvanizing has been around for nearly 200 years and, like paint, forms a barrier on ferrous metals to prevent galvanic corrosion -- the decomposition of iron to iron oxide through electrolytic charges in water. But, unlike paint, galvanizing provides a barrier of zinc crystals grown on the steel which combine with the steel in a very tough, abrasion-resistant (3600 psi adhesion) set of compounds. In addition, when paint is chipped, leaving bare ferrous metal unprotected to the elements, corrosion begins in the chip and will proceed through the material and under surrounding paint, causing bubbles and pinholes -- like you remember on the front fenders of Fords and Chevrolets of the 1950s. Galvanized material, however, even if chipped to the bare base metal will protect the base metal for years as the surrounding zinc actually forms a self-sacrificing anode in the electrolytic corrosion process. The zinc is formed into oxides before the steel is damaged.
"Detroit learned its lesson from those days when fenders rusted out over the headlights, because, today, the auto industry uses pre-galvanized sheet metal for many body components," Langemeier explained.
Why you should care
In many cases agricultural engineering tends to take corrosion control into account by "over-engineering," Langemeier says. "For instance, if a 1/4-inch tool bar thickness will work, but corrosion concerns threaten the useful lifespan of that piece of equipment, many times engineers will just specify larger or heavier material. The attitude being, 'Sell it, use it and let it rust.'
"Similarly, many operators will buy a piece of equipment and essentially expect it to rust, thinking, 'I'll just shoot paint on it when the time comes.' "
Langemeier knows farmers are proud of their equipment, and many are prone to certain "colors" identifying their brand when they have all that equipment set out by the machine shop. "If that equipment was all hot-dipped galvanized to start with, it would last longer, and you wouldn't necessarily expect to have to repaint it," he notes.
Painting a galvanized surface adds even more protection to the parent metal, and galvanizing actually helps paint last longer because tiny cracks and pores in the paint don't cause serious corrosion issues with the underlying zinc that otherwise might impede the integrity of the paint job.