The Sherardizing Process
Sherardizing is a thermal diffusion process and involves placing the pre-cleaned components to be coated into a container, along with a distribution media and a calculated mass of zinc powder.
The container is sealed and placed into a furnace which is raised to a temperature of between 330˚C and 425˚C in order to vaporise the zinc, allowing it to form an alloy with the substrate. At the same time, the container is rotated for a pre-determined length of time, usually between 2- 4 hours.
The resultant Sherardized coating is smooth, matt grey in appearance and uniform in thickness, the normal range being between 15 to 80 µm, although thicker coatings up to 100 µm are possible.
After the components have been Sherardized, they are normally cleaned and zinc passivated, making them ready for the application of additional coatings if required.
Sherardizing is a versatile process and component size and shape can range from small washers to larger, more geometrically complex and intricate components. As the components to be Sherardized have to be packed into a container, their size is limited by its dimensions of 2000mm x 500mm x 400mm.
Sherardizing - An Introduction
Corrosion costs, economically, environmentally and can ultimately lead to catastrophic failures. Corrosion protection is therefore essential in our industrial economy. Designers, specifiers and fabricators are constantly looking to use and develop the most effective and economic solutions, bearing in mind that every 90 seconds across the world, one tonne of steel turns to rust and of every two tonnes of steel produced, one tonne is to replace rust.
Zinc has been used for over a century to enhance the longevity and performance of steel due to its intrinsic resistance to corrosion. Almost half of the world's annual consumption of zinc is for protecting steel from rust.
Sherardizing - so called after its British inventor Sherard Cowper Coles in 1900, is a method of producing a long term protective Zinc-Iron alloy coating on iron and steel and therefore giving high protection against corrosion and abrasion. Sherardizing also produces an ideal surface for other processes such as rubber to metal bonding and the application of organic coatings, oils, stains, lubricants and sealants and provides a cost effective, high performance alternative to hot dip galvanizing.