What is ISO 17668 - Sherardizing - specification about?
ISO 17668 specifies minimum thickness requirements for six classes of zinc diffusion layers applied to ferrous products by the sherardizing process for the purpose of protection against corrosion and wear.
ISO 17668 specifies Sherardizing process specification for zinc diffusion coatings on ferrous products.
NOTE 1 For general information about post-treatments, see Annex C and Annex D.
NOTE 2 Individual product standards can incorporate this International Standard for the coating by quoting its number or can incorporate it with modification specific to the product.
Who is ISO 17668 - Sherardizing - specification for?
ISO 17668 on sherardizing - specification is useful for:
- Chemical industry
- Chemical laboratory
Why should you use ISO 17668 - Sherardizing - specification?
According to ISO 17668 guidance, sherardizing helps user by a thermal diffusion coating process in which ferrous particles are heated in the presence of a sherardizing mixture consisting of zinc dust with or without an inert material.
ISO 17668 helps to practice the process which is commonly performed in closed, slowly rotating or fixed containers at temperatures ranging from around 300 °C to 500 °C. The normal processing temperature is below the melting point of zinc (419 °C).
During the process, zinc reacts with the surface to form intermetallic layers on ferrous articles.
A coating thickness of 10 μm to 75 μm can be achieved. The coating thickness is accurately controlled by the amount of zinc dust, processing time and temperature. The coating closely follows the contours of the base material and uniform coating thicknesses are produced on articles, including those of irregular shape.
After sherardizing, the container load is cooled down. A screening process separates the sherardized articles from the unused sherardizing mixture. The articles, with the zinc-iron inter-metallic layers, are eventually post-treated resulting in a clean and passivated surface.
ISO 17668 is common to use articles coated with zinc-iron inter-metallic layers as a primer or base-coat for duplex-systems.