Press "Enter" to skip to content

Everything You Need to Know About the Galvanizing Process

Protecting steel and iron surfaces from abrasions and rusting is mainly done through the galvanizing process, which is discussed extensively here.The whole galvanizing process is simple once you have the right materials in place. The process entails coating iron or steel with the molten zinc to provide a protective layer over the metals. Other methods include electroplating, sherardising, and mechanical platting. The above techniques can be very tedious and may take an extended period. However, using the best galvanizing spray ensures that you get the best results with minimal effort.

All the processes mentioned above are aimed towards the same goal, but galvanizing is the most common method. Using the best galvanizing spray is one of the best decisions you will ever make when it comes to protecting your iron or steel surfaces. Let us have an overall look at the entire galvanization process.

Method of Preparation

The process begins by removing contaminants on the surface of the material you are working on. Contaminants may include rust, paint, scale, or even oil. Using abrasive blast to clean the surfaces may be necessary, especially if a large mill scale is involved. The main process you are going to go through include, fluxing, galvanizing, and finally quenching.

Fluxing

Once the surface has been cleaned with acid, the next step is to deepen it into a flux solution. The solution normally contains about 30% of zinc ammonium chloride, which is kept at a constant temperature of 650°C.

The main purpose of the solution is to remove any oxides on the steel surface, which might have formed during the avid cleaning process. Since the metal surface is highly reactive, the solution also helps to prevent further oxidation from taking place. Once you are through, wait until the steel surface is completely dry before galvanizing.

Galvanizing

Galvanizing is an elaborate process that entails immersing the steel surface in a molten bath of zinc. In the process, the molten zinc will react with the steel surface, and the result is a multi-layer series of an alloy consisting of zinc and iron. For the best results, it is recommended that you wait until the surface reaches the temperature of the bath which usually ranges from 450°C to 465°C.

Wait for a few minutes, then remove the steel from the bath while carefully observing the rate. You will notice that a pure form of zinc coating solidifies on the outer layer. The bathe time varies depending on several factors, but at least 15 minutes in the molten zinc bath are considered adequate.

The product you have after the galvanizing process comprises pure zinc and metal alloy of zinc and iron, all of which are chemically bonded to the steel surface. The coat is highly durable and will provide unrivaled resistance to abrasion.

Quench

The final process is to quench the steel in a solution consisting of mild sodium dichromate. This will help to prevent staining due to wet storage, which is usually experienced at the early stages of the galvanizing process.

Required Coating Thickness

The layers of the zinc-iron alloy usually form faster during the first few minutes once the steel is immersed in molten zinc. After that, the rate of alloy formation decreases drastically. As we have mentioned earlier, during the withdrawal process, a purer form of zinc will form on the outer layer of the steel. However, the amount of zinc coating that will build on the steel item is entirely dependent on the weight and thickness of the steel.

The minimum recommended zinc coating for a steel thickness of greater than 6mm is 600g of zinc for every square meter of the metal surface. That coating can be a bit thicker on the corners as well as edges. The thickness of the zinc coating is mostly influenced by two main factors, the condition of the surface you want to galvanize and the chemical composition of the metal.

The Condition of the Steel Surface

The most common method of increasing the surface area is grit blasting. By increasing the surface area, you increase the reactiveness of the metal to molten zinc. The higher the reactiveness, the thicker the coatings. However, it should be duly noted that making the surface slightly rough results in the poor appearance of the final product.

Chemical Composition of the Metal

The most common chemicals in steel include phosphorous and silicon. Both substances have significant effects on the galvanized material. Bigger coating thickness is likely to be witnessed in metals with a high composition of silicon between the range of 0.04 to about 0.14%. On the other hand, the growth rates are fewer in steel with a silicon composition of about 0.15% to 0.22%.

The normal threshold of phosphorus in steel is about 0.05%. Steel with phosphorous levels above the threshold is likely to increase the reactivity of the metal at a more rapid pace. It is also important to note that phosphorus, in combination with silicon, can produce a thicker galvanized coating, which may be undesirable.

Comments are closed.