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The enemy on my metal: corrosion and countermeasures

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Without corrosion protection, the service life of metal parts and components would be significantly reduced. Everyone knows the problem: things rust as soon as they are exposed to the weather for a short or long time. Automobiles, bicycles or household appliances would lose their “shine” in a very short time without appropriate pre-treatment and would be exposed to corrosion without protection. The term “corrosion” refers to the process of chemical or electrochemical damage to metals and their surfaces as well as any colour changes. This results in unwanted wear of metallic surfaces and degradation of organic material as well as deterioration of the condition, whereby not all metals are affected. For example, metals such as gold, aluminium, zinc, nickel and platinum are resistant to corrosion.
Triggers of corrosion include fresh and salt water, humidity, soil, air and pollution.
If further distinctions of corrosion are made, the following types can be classified:

Pitting corrosion
This corrosion forms small depressions or spots on the metal surface which, if untreated, can result in small or medium sized holes.

Selective corrosion
As the name of this type of corrosion suggests, corrosion only attacks certain parts of the metal. The starting point is the surface, whereby the corrosion progresses further into the interior of the material.

Surface corrosion
The best known form of this corrosion is rust (oxidized iron), which spreads over the entire surface of the coatings.

Intercrystalline corrosion
With this type, the surface is spared, so the corrosion spreads inside.

Tension and vibration cracks
The corrosion is caused by a corresponding stress or vibration on the material, connected to the respective output medium.

Gap corrosion
If metals are joined together and have a small gap or welds that are not gap-free, corrosion can occur at these bottlenecks.

Infiltration corrosion
This form frequently occurs in bondings with plastics, whereby corrosion does not take place on the plastic but on the metal and thus literally “infiltrates” the element.

The corrosion rate is the rate of material removal or change. This is measured in millimetres/year and depends on various factors, e.g. temperature, humidity, pH value and other complex influences.

Protective measures against corrosion

The best known method for protection against permanent corrosion is the galvanizing of metals. A corresponding zinc layer is applied to the material by melting baths, electrochemical compounds, spraying or diffusion in order to protect the material at low cost. Zinc plating is therefore one of the coating measures and requires appropriate pre-treatment of the material in the first step, e.g. by grinding, polishing, degreasing. The powder coating and the eloxal coating (anodisation) of stainless steel and aluminium promise alternatives to surface treatment. Powder coating allows numerous colour aspects to be taken into account, as well as the anodising process, whereby both methods also produce an optical upgrading of the metals (surface refinement). These methods are therefore particularly suitable for high-quality metal products, which are not least produced by Gronbach for the household sector and the automotive industry. In the next step, surfaces made of aluminium can be printed or engraved with a logo and graphics using a laser (aluminium finishing).

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GRONBACH is a manufacturer and system supplier of mechanical components, OEM devices and complex components made of aluminum, stainless steel and plastic for various industries. We offer our customers high-quality services as a full-service supplier, from mechanical production and surface finishing to hybrid technology and toolmaking.

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