Technical possibilities at Metoba
Metoba offers the following techniques for processing Aqueous degreasing :Reel-to-reel-finishingRack-finishingBulk-finishingKorbtechnik
1. Characteristics and properties
Boil-off degreases and electrolytic degreases are operated at temperatures of 40-70°C and contain basic salts and surfactants. The functional principle is based on the saponification of oils and fats of a non-mineral nature. This is controlled by temperature and exposure time. The surfactants absorb the detached oil and grease and permanently separate it from the workpiece surface. Here it must be ensured that the oils and greases can be saponified, i.e. they must not be thermally cracked, i.e. burnt in.
During cathodic degreasing, molecular hydrogen is produced on the surface of the workpiece, which “blows off” impurities. Since hydrogen can diffuse into the base material during this process, anodic degreasing is carried out afterwards, depending on the material. Molecular oxygen is produced on the surface of the workpiece, which also “blows off” the impurities and additionally combines with the possibly diffused hydrogen of the workpiece to form water, thus reducing embrittlement of the workpiece.
2. Benefits and areas of application
Aqueous degreasing represents the first and most important wet-chemical treatment step in the creation of a high-quality composite material. A distinction is made between aqueous degreasing, electroless degreasing and electrolytic degreasing. Electrolytic degreases are divided into cathodically and anodically switched degreases. In addition, electrolytic degreasing represents an important activation of the workpiece for the subsequent coating.
3. Basic material
So-called boiling-off degreasing is the only possible cleaning method for zinc die-cast and aluminium workpieces in weakly alkaline solutions, without damaging the base materials, which are sensitive to alkaline solutions. Non-ferrous metals, steels and stainless steels are pre-cleaned in strongly alkaline boil-off degreases, sometimes additionally with ultrasonic support, before they are electrolytically degreased. Electrolytic degreasing is also used for non-ferrous metals, steels and stainless steels. Non-ferrous metals are switched cathodically and then anodically, steels usually anodically and then cathodically.
4. Required delivery condition
Each basic material requires its own material-specific pretreatment, because degreasing is the most important pre-treatment step in the creation of a high-quality composite material. Only a completely oil- and grease-free surface of the workpiece makes the subsequent galvanic coating possible. The goods provided must be largely metallically bright. Residual oils or residual impurities must be removable with common aqueous alkaline degreases. Oils containing silicone, alkali/alkaline earth and high-pressure additives must be avoided at all costs.
Aqueous degreasing is usually the first step in galvanic processing.