Mild steel fabrications such as entrance gates, safety grills, rolling shutters, collapsible gates, sliding doors etc are known and used for their strength amd durability. They take a short time to be fabricated and can be quickly installed.
They however have a high initial cost and are meant to last a lifetime.
They however have a high initial cost and are meant to last a lifetime.
Mild steel has an achilles heel though and it is rust and corrosion. Expose to water, sunlight, dust and pollution cause the structure to corrode and loose its strength and its lifespan quickly shortens. The high initial cost comes to no avail.
It is wise thus to preserve the mild steel structure using anti corrosive paints and coatings.
Normal enamels and metal primers available in the market such as redoxide and zinc chromate primers are prepared using alkyd based binders. These binders typically have a lifespan of 1-2 years on exposure to the elements. The binder being the main film forming and barrier forming medium in the paint heavily influences the life of the paint. Due to the inferior quality binder, the regular enamels begin flaking and chip off in a short span of time, leaving a small area of mild steel exposed. Smaller areas of exposed mild steel corrode much faster and begin to rust. Rust being more voluminous than mild steel causes the paint in the area around the corroded spot to chip off, causing even more rust, snowballing into a much more serious problem.
To save your invested time and money, it is hence worth investing in a good quality coating for your metal structure. It is also worth following best practices while applying the coating.
To coat any mild steel structure, the following is the best coating procedure.
Start off by removing any corrosion or rust using a rust remover and if necessary use a wire brush. Pay special attention to weld joints and corners as these are the most stressed and are prone to rust. Apply a coat of epoxy based metal primer generously over the surface. Zinc phosphate based epoxy primers are the best ones as the zinc phosphate acts as an active rust inhibitor. Allow the primer to fully cure. Fill dents, crevasses and holes using a polyester based putty, commonly known as a body filler. Give ample time for the putty to set. Apply another coat of the zinc phosphate primer. Allow to cure. To finish the coating aesthetically and to build resistance to deterioration of the coating from exposure to UV, apply a polyurethane based enamel as the final coat. Apply 2 coats of the PU coating, typically using spray equipment.
The above treatment will provide an extremely durable finish and a long life to the mild steel structure.
Special care must also be taken to protect parts that are sunken in the ground. 2-3 coats of the epoxy zinc phosphate primer must be applied before installation. The primer coat must not be damaged during the installation.
Thickness of the coatings on parts that are exposed to hand and foot traffic must be built up using an intermediate hi-build coating to resist wear and tear.
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