The most environmentally friendly surface treatment, minimum carbon footprint, sustainable technology

How to ensure maximum protection for your steel?

Do you prefer the most environmentally friendly method of surface treatment?
Try the unrivalled method of thermal diffusion galvanizing – Sherardizing, offered by our company ERLEN

Benefits of Sherardising


It surpasses all other methods of anti-corrosion coating in many respects.


The hardest of all zinc coatings, able to withstand significant industrial pollution.


Uniform coating, ideal for smaller and irregularly shaped objects without adverse changes in the thickness of the protective layer.

Lower temperature

Lower process temperature range that prevents loss of mechanical properties and shapes of the parts.

Long lasting

Long-term durability, tested in salt chamber for 2500 hours.

Hydrogen free

Total elimination of hydrogen embrittlement.


Environmentally friendly – approaching a zero-emission process with no toxic substances.

Lower costs

Cost-effective in terms of initial protection costs, follow-up treatment and maintenance costs over the entire life cycle.

Sherardizing – Thermal diffusion galvanizing

Technology Description

The process of thermal diffusion galvanizing, also known as Sherarding, consists of diffusion filling steel objects with zinc. The reaction takes place in a rotating electric furnace filled with zinc powder at temperatures of 360-430 °C. The process results in the formation of an outer layer of zinc-impregnated steel on the surface of the protected steel objects. The surface layer thus formed is characterised by exceptional corrosion protection. The thermal diffusion method is also characterised by unrivalled abrasion resistance due to the absence of a deposited and therefore peelable layer. Due to the lower temperatures, there is no change in the internal steel structure and therefore this method is also suitable, for example, for the protection of springs and similar heat-treated elements.

The galvanising process is carried out in closed chambers in which the zinc diffuses into the steel structure. For this reason, the size of the chambers limits the maximum dimensions of the parts to be thermo-diffusion galvanised. We are able to offer our customers thermal diffusion galvanizing of parts with a maximum length of 300 mm. A special type of parts are bars, which we are able to galvanise up to 1000 mm in length and up to 10 mm in diameter. The maximum weight of the input is 250 kg. The structure of the surface layer resulting from thermal diffusion galvanizing consists of various intercrystalline compounds of zinc and iron.”

The resulting layer has a matt grey colour. Machine components can be realized with a guarantee of reciprocal mobility.

Corrosion Tests of the ERLEN Company

ERLEN, in cooperation with Accredited Testing Laboratory No. 1053, has demonstrated through pre-production and continuous corrosion tests that:

the thickness of the thermodiffusion layer at a level of approx. 35 µm is equivalent to the corrosion resistance of a layer 85 µm deep in the hot-dip galvanizing version; valid for corrosion aggressiveness class C5 (according to ISO 14713-1 – very high corrosive activity)
tensile tests according to ISO 6892-1 do not adversely affect the strength characteristics of thermal diffusion coated steels
metallographic analyses did not confirm a detectable effect on the microstructure both qualitatively and quantitatively (grain size, phase morphology, etc.)
the rolling abrasion test (calotest method) shows measurably better results in resistance to breakage compared to hot-dip galvanizing

Technical Support

Quality standards

ISO 17668:2016 – Zinc diffusion coatings on ferrous products – Sherardizing
American Standard Testing: ASTM B633, ASTM B695
Russian Federation Standard: GOST R 51163-98

Coating classes

In accordance with EN ISO 17668:2016, the thickness of the thermal diffusion coating is determined according to the following classes:


Coating Thickness Min. (µm)

Application Fields

Class 15


Normal indoor and outdoor environments

Class 30


Outdoor applications in more severe environments, or where there is a requirement for extended service life

Class 45


Highly corrosive and or abrasive environments, e.g. industrial or marine

FAQ – Questions & Answers


Parts of trailers

Production of truck trailers

Parts of pumps

BBA Pumps

Components and parts of chains



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