Types of Industrial Coating

For centuries, hot-dip galvanizing has been used to ensure the steel structure is resistant to corrosion for a long duration. The process comprises of coating iron or steel with zinc by immersing in a molten zinc bath at a temperature of about 450° C. As a result, the immersed iron or steel is covered by the molten zinc resulting in a metallurgical reaction between the two metals to form a series of zinc-iron / zinc-steel alloy layers. Over a period of time, the molten zinc forms a uniform thick coating that covers the corners, edges, and penetrates recesses for complete. This resultant coating protects the steel from external and internal harsh environments.

Hot dip galvanizing is among the simplest galvanizing methods, which is also environment-friendly and offers long-term resistance against corrosion for steel. It comes in use, specifically, when the aim is to attain corrosion protection without having to incur the cost of investing in stainless steel. It is one of the most efficient and cost-effective ways for imparting corrosion resistance to steel.

In mechanical galvanizing, a thick zinc layer provides cathodic or sacrificial protection for the steel fastener. Since zinc is more reactive than iron, the zinc coating first “sacrifices” or corrodes and protects the steel substrate. The rate of corrosion of zinc is at least 10 times slower than that of steel, so a thin layer of zinc can protect steel for a long time.

Mechanical parts can be treated with dichromate for color coding and phosphate stain to improve paint adhesion and waxing.

Mechanical zinc plating can be used on a wide variety of construction products including ASTM A325, A563 Grade DH construction bolts, heavy duty hex nuts, A307 bolts and studs, A449 hex bolts, F1852 tension control assemblies and F436 hardened steel washers, DIN 6914, DIN 6915, DIN 6916 and for bolts with small diameter, as well as fine-thread screws etc.

The electroplating process begins with a careful cleaning of the fasteners surface in detergent-type alkaline solutions, which is then treated with acid to remove surface rust or scale. Electroplating is carried out by on of the methods of electroplating such as silver plating, copper plating and chromium plating.

The fasteners are immersed in a chemical bath that uses dissolved zinc. When direct current is applied, the zinc metal in the anode begins to dissolve and the free metals reach the cathode to form a thin layer of lining over the fasteners. The thickness of the galvanizing depends on the galvanizing time, the current strength and the chemical composition of the bath.

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Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene with various uses, it is a fluorocarbon element since it is a high molecular compound composed entirely of carbon and fluorine.

High electronegativity of fluorine, fluorocarbons with London dispersion forces. It has one of the lowest coefficients of friction of all solids and is used as a non-stick coating in pans and other cookware. It shows a significantly lower reactivity, partly due to the adhesive strength of CF, and is therefore mainly used for the storage of reactive and corrosive chemicals in containers and pipes.