The use of galvanized steel on the farm is very old. It started over 150 years ago with zinc buckets and tubs at the time when stables were mainly furnished using wood and stone. During the last 70 years, galvanized steel has been used almost exclusively for these as well, and buckets have since been made of plastic.
Often the structure of the barn is also already hot-dip galvanized. After all, mechanization created a need for economies of scale, stables became bigger and bigger. Steel is then the construction material of choice to make large spans possible without limiting the floor area by masonry and wood. Furthermore, steel is easy to machine and weld, and profiles are standardized, making strength calculations easy to perform. In addition, steel is readily available and relatively inexpensive.
Because there is also a downside to steel, the steel is hot-dip galvanized. Without proper protection, the steel would rust immediately. Wet coating and paint provide inadequate protection to the underlying steel in a barn. In addition, if the paint layer is damaged, rusting will begin again immediately. Under rust (rust under the paint layer) often occurs and the structure gradually loses its strength. With hollow profiles, there is also the chance that rust from the inside of the tube will have damaged the tube to such an extent that it will suddenly fail, with all its consequences.
In fact, hollow profiles are also zinc-coated on the inside during galvanizing, providing a reliable and safe construction.
The steel is discontinuously hot-dip galvanized in a so-called contract galvanizing plant. The galvanizing plants in the Benelux work according to the international standard EN ISO 1461. This standard describes what the zinc composition must comply with, what layer thicknesses are possible and how the end product must be assessed.
In order to produce a product suitable for hot-dip galvanizing, a number of things must be taken into account.
Important are the dimensions, thickness of the steel, the welding and the galvanizing holes that are required. Recommendations and guidelines for this are described in EN ISO 14713-2.
Galvanized steel lasts a very long time. The reason is that zinc corrodes but; unlike rusting steel, after some time the corrosion products form a patina layer from basic zinc carbonate. That formation of a patina layer takes from a few days to about 3 weeks and the buildup of the zinc patina layer continues to grow for up to 12 months after galvanizing.
This zinc patina layer is very important because it seals off the entire zinc surface from the atmosphere. When this layer is formed, then the layer is resistant to most dry substances and also liquids with an acid number of 5.5 to 12.
However, should the zinc layer remain continuously moist with products such as ammonium, sulfates and/or chlorides, the zinc layer may be affected. This situation can occur with barn manure. In the event that the barn is not emptied frequently enough and/or the galvanized steel is left unprotected in the barn manure, additional measures are required. If possible, place the galvanized steel barn equipment on a concrete elevation that avoids direct contact with manure as much as possible. In addition, ensure that the barn is sufficiently frequently emptied and cleaned.
In addition, a suitable coating could be applied to the zinc layer in the area of the manure up to approx. 30 cm above it. A plastic sleeve should also be used around the galvanized profiles to protect the zinc layer from the aggressiveness of the manure.
Bolts, nuts and washers should be at least hot-dipped galvanized or stainless steel. Avoid using galvanized bolts, nuts and washers from the hardware store. These have far too low a zinc layer thickness and will corrode and rust far too quickly.
The raw material zinc will be available for many years to come, but currently a lot of zinc is already being recycled. When melting zinc-coated scrap metal, the zinc is collected separately. Zinc-containing residues are also released during galvanizing, which are reused in a variety of materials, from cosmetic products to gutters. The best part is that a product is simply re-galvanized after decades of use. That way, only a fraction of energy is lost compared to remanufacturing the barn equipment. Almost all galvanizing plants in the Benelux have facilities to reapply that protective zinc layer to your products. At the time of writing this publication, the Department of Public Works has started a trial in which galvanized crash barriers are being re-galvanized and installed.
Reports of environmental pollution from heavy metals could easily give the impression that zinc is a hazardous substance. Nothing could be further from the truth. Zinc is an essential component for several biological enzymes and an intake of max 15mg per day has been stated as a safe value. Zinc is an important catalytic component of many enzymes. It is a trace element; extremely small amounts of the element are sufficient to make these enzymes function and thus make life possible. Zinc oxide as released from the zinc surface is a commonly used substance in zinc ointment, among other things, but many sunscreens also contain some fraction of zinc oxide. Many other cosmetic items also contain zinc oxide because of its beneficial effects on eczema and other skin conditions. Also, don’t forget the dietary supplements (From A to Zinc) that many people take every morning.
NEN EN ISO 1461
Coatings applied by hot-dip galvanizing to iron and steel objects – specifications and test methods.
EN ISO 14713 PART 2
Zinc coatings – Guidelines and recommendations for the protection of iron and steel in structures against corrosion – Part 2: Hot dip galvanizing
