Ever since steel was discovered, people have been trying to find ways to prevent it from rusting. From kitchen utensils to cladding on skyscrapers, from car bodies to steel rebar, rustproofing is a necessity when it comes to maintaining an object’s aesthetic and structural integrity. Pallet racks are no exception, but to fully understand the importance of rustproofing them, we must first look at what rust is exactly.
In technical terms, rust is a type of corrosion that involves iron (the main component of steel), an electrolyte, and an electrical potential difference (i.e. an anode and cathode). During the rusting process, oxygen atoms from the atmosphere are reduced to hydroxide ions which are transferred through the electrolyte thanks to the potential difference and react with the iron ions to form iron oxide, more commonly known as rust (1). To put it in layman’s terms;
Steel + Water + Oxygen = Rust
Looking at this equation, it is then easy to see why installing pallet racks outside can be risky. Anyone who’s been camping knows that the great outdoors has an abundance of two things: fresh air and rain/humidity. However, detrimental rusting of steel does not only happen outside; it will occur even in an environment with a relative humidity greater than 70% (2).
Let’s pause for a second because some of you might be saying to yourselves, “that’s a nice equation and all, but why exactly is rust inherently bad for my structure?” The answer is quite simple and intuitive: when steel rusts, the iron in the steel is being converted into iron oxide. What’s happening is that steel, one of the strongest and widely used building materials, is being replaced by rust, something you can crumble between your fingers. The material supporting all the pallets above it is being replaced by…dust! Given enough time, any unprotected pallet rack will slowly but surely be eaten away by rust.
So, what can be done to prevent this? Well, a very common solution is to paint the steel. Great! Most pallets racks already come painted. Unfortunately, paint is probably the least effective way to prevent rust because of how easily it is scraped or chipped off, through contact with pallets or lift trucks. In fact, it is even designed to flake off when the steel is deformed, leaving the steel fully exposed and vulnerable. Unlike a dip process, the powder coated paint won’t necessarily penetrate to reach every nook and cranny leaving some areas uncovered and unprotected.
The only truly effective way to prevent rust on a pallet rack is to use galvanized steel. Galvanizing is the process of immersing steel in a bath of molten zinc. The zinc and the iron react to form a tightly bonded alloy coating. This zinc coating protects the steel in two main ways: by barrier protection (like how paint protects steel), but more importantly by cathodic protection, the process of adding a metal that is more anodic than iron so that it will corrode in the place of steel (3). Zinc is essentially sacrificing itself to save the steel beneath it. The bonus is that zinc corrodes much slower than steel, and for that reason galvanized steel will, on average, corrode at 1/30th the rate of regular steel (4). This allows the steel to focus all its energy on supporting those precious pallets and goods. In this endless war against the tyranny of rust, zinc’s heroic act is truly deserving of the Metal of Honor.
(1) Corrosionpedia Inc. (2017). Rust. Retrieved from: https://www.corrosionpedia.com/definition/992/rust
(2) Turner, D. K. (2017). Tips on Painting Structural Steel. Retrieved from Canadian Institute of Steel Construction:https://dir.cisc-icca.ca/solutions-centre/technical-resources/technical-resources/coatings/tips-on-painting-structural-steel?lang=en-CA
(3) American Galvanizers Association. (2017). Corrosion Protection. Retrieved from www.galvanizeit.org: https://www.galvanizeit.org/hot-dip-galvanizing/why-specify-galvanizing/corrosion-protection
(4) American Galvanizers Association. (2017). How Long Does HDG Last? Retrieved from www.galvanizeit.org: https://www.galvanizeit.org/hot-dip-galvanizing/how-long-does-hdg-last