Contact with us


Zinc Thermal Diffusion

Zinc thermal diffusion (thermal diffusion zinc coating, sherardizing) is a technological field in which we - Promet S.A. - are a European leader. We use it every day for the protection of nails with thermal diffusion zinc coating.


Thermal diffusion zinc coating is an innovative technology used for the protection of nails and other small steel or cast iron elements against corrosion. Coating applied using this method demonstrates very effective anti-corrosive properties, such as high resistance to abrasion and mechanical damage. 

The process of diffusion coating of metals takes place in hermetically sealed cylinders placed inside an electrical furnace. The cylinders contain zinc-coated elements and an appropriate quantity of a mixture of zinc powder. The resulting diffusion processes result in the creation of a zinc-iron alloy coating, which demonstrates very high anti-corrosive properties.

Because the process takes place in temperatures much lower than hot-dip galvanising, it can be used for the zinc coating of elements that may become tempered in the process of hot-dip galvanising, without risking the loss of their mechanical properties. Additionally, the created coating perfectly reflects the shape of the processed element, without any protrusions or build-up of material that may occur during hot-dip galvanising.

Elements treated with zinc thermal diffusion do not require any pickling before the zinc coating process. Because of this they are not exposed to hydrogen embrittlement.

Additionally, the absence of pickling during the preparation of surfaces before zinc coating and the absence of chromates in the process of passivation of the elements after zinc coating means that the process is very environmentally friendly. No toxic waste emission.


Promet S.A. is one of only a few companies in Poland that provide professional zinc thermal diffusion services and is a European leader in this field. We have the most advanced zinc thermal diffusion line in Poland. We have the appropriate machinery and experience to provide zinc thermal diffusion services for our clients.

Our nails can be ordered either without any zinc coating, or with thermal diffusion zinc coating.


Collating methodPaper tape collated nailsPlastic strip collated nailsWire collated nailsNails in bulk
  Length   50 mm - 90 mm 50 mm - 90 mm
 carpentry nails: 
 40 mm - 70 mm
 32 mm - 100 mm 32 mm - 180 mm
  Diameter   2,8 mm - 3,1 mm 2,8 mm - 3,1 mm
 carpentry nails: 
 4,0 mm
 2,1 mm - 3,4 mm 2,1 mm - 6,5 mm
  Shank    smooth; ring; pattern;  smooth; ring; pattern; spiral  smooth; ring; pattern; spiral  smooth; ring; pattern; spiral; Swedish square; straight square
  Standard   PN-EN 13811