Coatings and Surface aspects

Coatings

Three types of metallic coating are available:

  • Pure zinc. Galvanised steel (GI) is coated with an almost pure zinc coating (>99% zinc)
  • Zinc-iron alloy. Galvannealed steel (GA) is coated with a zinc coating containing approximately 8-12% iron
  • MagiZinc Auto. MagiZinc Auto steel (ZM) is coated with a zinc coating containing additional magnesium and aluminium.
     

Coating weight

Coating

Minimum

Maximum

Pure zinc (Z)

100 (7 µm/side)

600 (42 µm/side)

Zinc-iron (ZF)

100 (7 µm/side)

140 (10 µm/side)

MagiZinc (ZM)

70 (5 µm/side)

200 (14 µm/side)

Coating weight measured in g/m2 double-sided (µm, per side).

Surface condition

Surface condition complies with standard: EN 10346:2015. Galvanised steels are available in surface conditions with minimised spangle MB or MC. Galvannealed steels and MagiZinc Auto are available in surface conditions B or C.

Surface condition B: improved surface, suitable for unexposed parts

With this surface condition, small imperfections such as stretch levelling breaks, skin pass marks, slight scratches, indentations, surface structure, zinc run-off marks and light passivation stains are permissible.

Surface condition C: best quality surface, suitable for exposed parts

Surface condition C is obtained by skin passing. The controlled surface for the exposed side enables application of a uniform paint finish. The reverse surface has, at least, the characteristics of surface quality B.

Surface finish

Galvanised (GI) grades with surface condition MC are available with different levels of surface finish. For exposed body panels with stringent paint appearance requirements we offer ‘regular’ surface finish. For panels with the highest paint appearance requirements we recommend the premium surface finish Serica®.

Surface roughness

Metallic coated steel for automotive applications can be supplied in various grades of roughness to comply with individual customer norms. If no roughness is specified, roughness will be as shown in the table below

Roughness Ra (µm)
cut off 0.8mm cut off 2.5mm
0.6 - 1.9 0.7 - 2.2

​​​Surface treatments

The surface treatments available are oiling and T-treatment.

Oiling (O)

The material surface can be oiled with preservative oil. Other types of oil - for increasing strength or reducing weight – are available to help achieve your optimum performance parameters. Please contact us for details.

Tata Steel offers the following range of oiling levels:

Coating type Oiling level
Pure zinc (GI) 0.25 - 1.7 g/m2
Zinc-iron(GA) 0.5 - 1.5 g/m2
MagiZinc Auto(ZM) 0.25 - 1.0 g/m2

Other oiling levels are available on request.
 

T-treatment

Please contact us for further information.

Prime Lubrication Treatment (PLT)

Prime Lubrication Treatment facilitates the manufacturing of stamped components by minimising known issues in stamping and joining.

For further information please visit our dedicate Prime Lubrication Treatment (PLT) page.