Galvanization Process

Metals such as iron and steel are prone to corrosion and to protect them from getting corroded, people make use of a process called galvanization. The process, is a metallurgical process, wherein, zinc is melted and used to coat iron or steel. It is also known as hot dip galvanizing process, where the coating of corrosion protection is given from one mil to just over four mils thick. Once applied, the zinc reacts with the coated metal and form what is known as zinc carbonate. This process not only makes a metal resistive of corrosion, but adds to the strength of the metal, as well. This is the reason a galvanized metal tends to be thicker than the uncoated one.

Basic Facts About Galvanization

Most house siding bear those ugly and unpleasant sight of staining nails and screws. This is because the metals are not galvanized. It is obvious for such non-galvanized metals to cause dark stains on the siding, when they are attacked by corrosion. It is not only about unsightly staining, corroded nails and screws may also lead to deteriorating metal fasteners. So, one simple solution for all such problems is provided by galvanization.

So how does this hot dip galvanizing process go about. Here, the metal is given a hot bath of molten zinc, kept liquefied at a temperature of about 860 degrees F. So, the to-be-galvanized metal is simply given a dip into this molten zinc or fed through the zinc bath. But this step is preceded by some other steps and again followed by some finishing procedures. Know about each of these steps in brief, from the following.

The very first step in preparing the metal to be galvanized, comprise removal of oil, grease, dirt and soluble markings from the surface of the metals. For this cleaning procedure, a hot alkaline cleaner is employed.

Following this is a step known as pickling. Here the metal is chemically cleaned and prepped for the hot dip by using a diluted solution of hot sulfuric acid. This gets rid of the surface rust and mill scale.

Then comes fluxing. On top of the zinc bath, there floats the flux (which is zinc ammonium chloride solution). So, the metal is made to pass through this flux. The aim of this process is to remove oxides and prevent any oxidation of the metal before it gets galvanized.

Having gone through the fluxing part, the metal is now ready to be galvanized, which has been mentioned about, earlier. Post this, the galvanized metal is dipped into a dilute chromate solution. This is to provide a long lusting luster to the treated metal. Apart from this, this process, known as quenching, also helps to reduce the temperature to encourage immediate handling and inspection.

Then comes quality check or, in other words, inspection; the final step in the galvanizing process. Coating thickness, uniformity, adherence and appearance are the parameters which are inspected in order to ensure compliance with the specifications.

So these were the steps involved in a galvanization process. Similar to this is what is known as an electro galvanizing process. Here, the primary metal is virtually impregnated with zinc. The metal is coated with thinner, tighter-bonding coat of zinc with the help of electroplating (coat with metal by electrolysis). A zinc compound is exposed to an electric current, thereby, making the zinc ions positively charged. These ions then, establish a more secure bond with the primary metal, thus, providing a somewhat stronger tensile strength. However, the electro galvanizing process tends to be inefficient for materials which are constantly exposed to elements such as salt water.