THE South African Institute of Marine Engineers and Naval Architects (SAIMENA) is collaborating with the International Zinc Association (IZA) to promote zinc thermal spraying for the local ship-repair industry. “We have excellent local expertise to assist SAIMENA in realising its mandate of growing a vibrant, skilled marine engineering sector,” comments Simon Norton from the IZA Africa Desk.
SAIMENA is the professional body driving the growth and upskilling of the South African marine engineering sector, and is working hard to bring new and advanced expertise to the fingertips of the marine engineering profession.
“We continue to advance and promote maritime engineering knowhow and continuous development for marine engineers, ship repair engineers and designers. Working with professional bodies such as IZA enhances our capability,” comments Rear Admiral (JG) Kevin Watson (ret), President of SAIMENA.
Zinc thermal spraying can be applied to a variety of steel ships, from trawlers to warships, fast patrol boats and fisheries patrol boats. This includes superstructures, fittings and onboard steelwork which after zinc thermal spraying can be further coated by the application of a zinc rich primer and an epoxy coat to give a superb long lasting duplex coating system.
The advantage of zinc thermal spraying is that it is possible to apply zinc coatings of varying thickness but typically to about 100 microns. Spraying allows the thickness of the coating to be controlled and varied, even on different areas of the same structure and/or parts.
Thermal spraying makes it possible to apply zinc coatings to structures and components that are too large for hot-dip galvanizing or have to be zinc coated in situ. The metal coating is laid down in a single application. Zinc coatings also have excellent adhesion to steel and resistance to abrasion, enabling the structure to withstand rough usage. However, most of all they provide a barrier to the environment and offer galvanic protection to the steel.
All grades of steel, including highly alloyed steels, can be thermal spray coated. Spraying does not affect the metallurgical structure of the steel. Since zinc adheres and coats instantly, no drying time is needed. Designated top coating operations can start immediately, whereas paint systems in comparable categories might require days for cure.
In terms of lifecycle costs, Norton explains that the initial coating application costs are minimal compared to the maintenance costs over the life of the structure. Continuous maintenance is not required with a properly applied zinc thermal sprayed coating. A single application provides excellent corrosion protection, including areas where minor mechanical damage may have exposed the steel. Further application of organic epoxy top coats makes for an outstanding corrosion protection system.
The IZA’s collaboration with SAIMENA forms part of a long-term strategy to promote the advanced upskilling of South African engineers, the growth of the local maritime industry, as well as increasing the uptake of zinc in industry, where its primary application is for the corrosion protection of steel. Since the closure of the country’s only zinc refinery in 2011, it has been heavily reliant on costly imports, a situation that the IZA Africa Desk hopes to turn around by campaigning for the establishment of a new local zinc refinery.
“This is especially important given the ambitious infrastructure delivery programme plan being promoted by the government, which will require large tonnages of zinc coated steel,” notes Norton.
“Our association with SAIMENA is an example of how we are reaching out to the various professional bodies and associations to promote the benefits of specialised processes such as zinc thermal spraying,” concludes Norton.