Technical possibilities at Metoba
Metoba offers the following techniques for processing Zinc coating :Bulk-finishing
1. Characteristics and properties
Zinc is a bluish-white, brittle metal which, when polished, has a chrome-like lustre and is very brittle at room temperature and above 200°C. Zinc is a metal which is very brittle when polished. However, between 100°C and 200°C it is quite ductile and can easily be deformed. The electrochemically base zinc offers excellent corrosion protection on steels due to its low normal potential of -0.76V to iron with a normal potential of -0.44V and offers anodic protection to the underlying steel.
Zinc coatings are resistant to humid air, but oxidize rapidly on the surface and form white rust, which passivates the zinc layer. Zinc is not very resistant to alkaline and acidic media as they attack and dissolve it.
2. Benefits and areas of application
Zinc is one of the most important non-ferrous metals and, in addition to its use as a base material for die-cast zinc workpieces and as an alloying element, e.g. for brass, is of great importance for the corrosion protection of steels. Further areas of application for zinc are gold alloys, batteries, zinc sheets and the production of zinc compounds such as zinc chloride and zinc oxide.
Electroplated zinc coatings are ideally suited for mass-produced products such as screws, fasteners, stamped parts as well as for all workpieces where corrosion protection is paramount. The zinc layers applied in our company are glossy, have an average hardness of 100 HV 0.1 and are relatively ductile. In order to obtain correspondingly high corrosion protection values, layer thicknesses of 5-25µm are recommended. The corrosion resistance is specified in DIN 50960. A heat treatment to avoid hydrogen embrittlement of steels with a strength >1000N/mm2 is also possible in our company.
Zinc coatings offer a special protection for steels by the fact that even after the coating has been damaged by mechanical effects, the exposed steel remains protected from corrosion in the immediate vicinity of the damaged zinc coating.
3. Basic material
Steels are ideally suited for direct electrolytic galvanizing. With the acidic process we use, it is also possible to galvanize hardened steels and cast steel parts without any problems. Hardened steel requires additional heat treatment. Other base materials can also be coated after appropriate pre-treatment.
4. Required delivery condition
The goods provided must be largely metallically bright. Residual oils or residual impurities must be removable with conventional aqueous alkaline degreasers. Oils containing silicone, alkali/alkaline earth and high-pressure additives must be avoided at all costs.