Applying the hot dip galvanising process to steelwork provides products with a robust, durable and corrosion protective finish. This will last for many years without maintenance of any sort. The process itself has a number of stages that are required to achieve the galvanised finish. Forfar Galvanisers are able to omit 2 stages of the traditional galvanising process due to the advanced technology in our plant. This makes the whole process more time efficient and making the experience smoother for the customer.
Inspection and Hanging the products
The steel is checked to ensure it’s suitable for galvanising — free of paint, oil, or heavy rust layers that could interfere with the process. The products are hung at an angle to ensure a safe process – allowing zinc to flow down and out.
Automation
FGL have automated cranes that take products between each of the following stages.
Degreasing
The steel is cleaned. The process of producing a surface which is not contaminated with oil, or grease based products. This can be carried out by coating the ungalvanised products with either an acid or alkaline based proprietary product.
Rinsing
After degreasing, the steel is rinsed in water to remove any leftover chemicals. This stage of the galvanising process is omitted within the Forfar plant, making the whole galvanising process smoother and time efficient.
Pickling
The steel is dipped in a bath of dilute hydrochloric or sulfuric acid to remove rust and mill scale. It will remove oxidation (rust) from the metal surface, making the surface clean and able to react with the molten zinc.
Rinsing
A rinse to clean off any acid residue from the pickling stage. This part of the process is vital to the Galvanising process as the rinse removes and possibility of contamination in the next chemical bath.
Fluxing
The steel is dipped in a flux solution (usually zinc ammonium chloride) to prevent oxidation before galvanising and improve zinc bonding. Or it can be done by using a layer of the chemical which floats on the surface of the molten zinc bath. This is normally used at between 50C and 70C, which helps the steelwork to dry after it is withdrawn. Drying is important as it helps prevent zinc splash and a separate drying stage is sometimes employed.
Drying
This process is also omitted at FGL due to the advances in technology within the Forfar plant.
Hot Dip Galvanising
The clean, dry steel is dipped into molten zinc at around 450°C. The zinc reacts with the steel to form strong, protective zinc-iron alloy layers. The clean steel is immersed in the zinc and while it is submerged it alloys with the iron in the steel to form zinc/iron alloy layers. These layers form the basis of the coating, which is then covered with free zinc, as it is withdrawn from the galvanising bath.
Cooling & Draining
After dipping, the product is cooled by quenching in water, inspected for defects.
Final Inspection
Each piece is checked to ensure full coverage, proper thickness, and no sharp edges or defects — ready for decades of rust protection! It is then stored until ready for collection or delivery. Take a look at some recent products in our yard.
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