The surface finish of tinplate and coated laminate products is determined by the use of the appropriate finishing work rolls in each case. These rollers are used during the final stages of hardening by cold rolling, and in the case of tinplate, by the weight of the applied tin coating and its momentary melting.
The finishes applied on the base steel, defined in terms of surface roughness, are the most important:
Soft : Finish with surface roughness not exceeding 0.35 .
Stone (Stone): Finish characterized by a linear surface texture, parallel to the direction of grain (or laminate), with surface roughness from 0.35 to 0.65
Fine Stone: Variation of stone (stone) finish, with better resistance to corrosion, and surface roughness from 0.25 to 0.45
Shot blasting : Non-directional rough finish, available in various degrees of surface roughness. When the surface roughness is greater than 0.90 , the finish is known as Silver Finish .
The following table summarizes the different types of final finish of the material, with its identification code, the finish of the steel base, the type of material in which it is used and whether or not momentary fusion is used.
Momentary fusion is a process in which the tin coating melts first and then cools rapidly to produce a bright reflective appearance.
1º.- The standard finish is the stone, that is, the most used.
2º.- The brilliant finish is usually only available in a limited range of tinplate specifications.
3º.- In order to measure the surface roughness, it is necessary to unseal the sample chemically before its measurement. The measurement test is carried out transversely, ie at right angles to the rolling direction.