Because the anchor bolts used with light poles are typically exposed to the natural elements, they are almost always hot-dip galvanized. Galvanizing offers an exceptional corrosion resistant zinc coating for anchor bolts and other fasteners. The process provides durability, longevity and is an economical option compared to other types of corrosion resistant coatings.
Not all galvanizing is created equal. When it comes to galvanizing anchor bolts for the lighting industry, it is crucial that the bolts are galvanized in a system that is specifically designed for threaded fasteners. There are many galvanizing plants that are not designed for threaded parts, in which case the zinc can build up on the threads, making it impossible to fit a nut onto the bolt. The process of hot dip galvanizing fasteners does not rest solely on the dipping process either; the preparation and cleaning process before the bolts are dipped is just as important to having a successful finished galvanized product.
Preparation & Cleaning
- The bolts are lowered into a caustic soda solution for a designated amount of time in order to remove any oils from the cutting process and other organic materials which may be on the bolts before galvanizing. The bolts are then quickly rinsed in water.
- After the caustic soda solution, the bolts are placed in sulfuric acid in order to score the surface of the steel which will allow the zinc to actually penetrate the surface layer of the bolt and then they are rinsed with water a second time.
- The final stage of preparation involves a flux solution which the fasteners are submerged in to create the reaction the zinc will have to the steel.
Hot-Dip Galvanizing
- The galvanizing process requires the bolts to be completely submerged in molten zinc for a designated amount of time depending on the diameter of the material, grade of steel and a variety of other factors. The time in which the fasteners are submerged will allow the zinc to metallurgically bond with the steel.
- The fasteners are lifted out of the molten zinc while it’s still hot and spun in a centrifuge-like spinner to remove any excess zinc from the threads. This is key to ensure the nut fit and is considered the highest quality of zinc coating for threaded fasteners.
Inspection
- The fasteners are cooled in a water tank after the excess zinc is removed which allows for immediate handling.
- Every part is individually inspected to make sure that all of the excess zinc was removed in the centrifuge and that a nut will fit without issue. The bolts are then packaged and clearly marked for identification.