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Keeping corrosion at bay

Keeping corrosion at bay

By Huned Contractor

Mumbai-based Effco Finishes & Technologies (P) Ltd has quietly ushered in a revolutionary change in the surface coating process for fasteners used in the automotive and other sectors with the introduction of a zinc aluminium flake coating process that is free of hazardous substances and may become the norm of the future


Any fastener such as a flange bolt, combination screw or a hex nut may just be a small item in size but, as is known, it makes for one of the most crucial parts in the assembly of any product. And keeping in mind the increasing requirement of good reliable fasteners, SKS Fasteners was set up in Chakan near Pune in 1998. But that’s not the story. The most interesting aspect of a visit to this factory, headed by its director Sudhanshu Bindal, is the fact that it has commissioned the largest zinc aluminium flake coating facility in the country with an output of 400 tonnes per month.

“We have done this at considerable cost just so that we can have a leading edge in providing fasteners that don’t corrode easily. This is to primarily match the requirement of the automotive sector considering that OEMs like Tata Motors and Mahindra & Mahindra are now insisting on using such fasteners,” Bindal says.

The water soluble zinc flake coating technology, introduced in India by Mumbai-based Effco Finishes & Technologies (P) Ltd, is used for threaded hardware and metal parts in automotive and engineering construction and offers direct cost saving by not using solvents compared to other solvent-based products. “These water-based coatings are environment-friendly and free of any hazardous substances. Also, they help do away with the problem of effluent discharges and are suitable for all kinds of rugged weather conditions,” says Kalyan Dhakane, the company’s managing director.


Effco represents in India the products and technologies of Premium Products Inc., USA, Greenkote Plc., Israel and Junhe Technology Company Limited, China, for various specified proprietary coating technologies, coating plant and equipments, process application engineering know-how, etc. The zinc aluminium coatings are made through a combination of zinc and aluminium flakes in an electrically conductive binder system with integrated lubricants for adjusting the co-efficient of friction. The aluminium flakes help to reduce the build-up of white oxidation. The zinc flakes coatings are non-electrolytically applied as per the ISO 10683 and ASTM F1146 standards through mechanical application techniques with a combination of organic or inorganic top coat sealers.
Explaining how this technology is superior to the conventional electroplating process, Dhakane says that the zinc aluminium flake coating offers high-performance corrosion protection for bulky metal components, thereby enhancing the life of the complete protective system.

For such coatings, the thickness ranges from 5-15 microns and the corrosion resistance can be achieved over 1,000 hours by ASTM B117 in a salt spray test. “It is also free from hydrogen embrittlement and has anti-freezing properties along with heat resistance of 150 degrees Celsius through organic and 200 degrees Celsius through inorganic sealer top coats,” Dhakane adds.

The coating can be applied for high tensile fasteners, bolts, nuts, rivets, screws, springs, clips, clamps, brackets, brake discs, brake drums and brake rotors in the automotive, wind turbine, railways, energy and infrastructure sectors, among others.


An additional advantage that is now making companies like SKS Fasteners move towards zinc aluminium coatings is that these cut down on the use of water to a huge extent, have a low volatile organic content and remove the dangers of air pollution, thus making the production environment absolutely safe for the floor workers. “The coating meets ELV, WEE and ROHS guidelines for not using hazardous and declarable substances. It can be applied with non-electrolytically applied dip sin coating technique for mass produced hardware parts and by spray application with or without electrostatic for larger metal parts,” Dhakane informs.

So how did this technology come into being? From 1975 to 1978, similar electro-deposition systems were being sought with a significantly higher level of corrosion protection in response to the continually increasing quality requirements of the car industry. The development of non-electrolytically applied zinc flake coatings, which originally contained hexavalent chromium, also began at this time. The beginning of the eighties saw the emergence of chromium-free systems, which could also be applied at low stoving temperatures (substrate temperatures from 180 to 200 degrees Celsius). Organic and inorganic-based top coats were developed because of the specific properties of the zinc flake coatings and the fact that these could not yet be coloured.


The combination of base and top coats satisfied a large number of industrial requirements which previously could not be fulfilled. But the development of novel application methods was vital to make optimum use of this new technology. Thus, today, modern computer-controlled coating systems can be used for almost all types of parts.

Evidence of this computer-controlled zinc aluminium coating process can be found at SKS Fasteners where human interface has been kept to the minimum. “Gradually all manufacturers will shift to this coating technology and we have therefore taken this initiative to gain from first-mover advantages,” Bindal states.


For Dhakane, these are interesting times for his company with a lot of inquiries coming in for the zinc aluminium coating technology. “Today the finishing industry needs high-performance finishes that also take care of the environmental aspects
of mass-produced hardware metal parts. We are therefore the pioneers in terms of providing a substitute for the existing electroplating system that does not comply with any of the new environmental norms,” he says. With almost two decades of experience in the surface coating industry, Dhakane also provides a kind of one-stop shop solution by putting up turnkey projects for those who would like to change over to zinc aluminium coating. “We already have companies like Hyundai, Ashok Leyland, Piaggio, Ford, Kia Motors, Volvo and others as our clients. And this is just the beginning,” he predicts.

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