Washing and cleaning of grease on metal parts

It can be a final surface finishing operation, to present the part in the best possible condition, or an intermediate finishing, prior to a final finishing treatment such as painting, galvanizing, etc.

Main types of degreasing

Mechanical degreasing

• • Manual: cloths, sponges, brushes or brushes impregnated with product.
  • Centrifuge: removes oil by centrifugation.
  • By abrasion: using the impact of abrasives on the metal surface by blasting, shot blasting, vibrating machines.

2. Spraying: apply the degreasing product under pressure on the surface of the parts to be cleaned.

3. In vapor phase: it is based on the creation of a vapor flow that condenses on the surface of the parts to be degreased, dragging the oily layer.

4. Immersion: refers to the placement of the parts in a tank with the degreasing product; there are different types:

• • Rotary drums
  • Ultrasonic agitation
  • Electrolytic immersion
  • Cold or temperature immersion

Main washers for grease cleaning

Nowadays there are a large number of technologies with which to carry out a cleaning and degreasing process of metal surfaces. These include:

• Parts washing tunnels
• Solvent washers
• Washing machines with cochlea
• Ultrasonic washing equipment
• Hydrokinetic washing machines
• Rotary table washers

If necessary, washing machines can be designed to combine different stations and stages and to incorporate other processes.

Main types of degreasers

• Aqueous alkaline solutions: consist of a mixture of different sodium or potassium salts with detergents (surfactants) and additives such as glycol ethers and chelating agents. They have the ability to remove both organic and inorganic contaminants adhering to metal surfaces. Between 80-90% of metal surface cleaning applications can be carried out with these types of solutions.
• Acid solutions: consist of mineral acids, organic acids or acid salts in combination with surfactants and corrosion inhibitors. This type of solutions can be applied in degreasing processes by immersion including electrolytic immersion, by spraying or manual, with or without heat.
• Non-chlorinated organic solvents: group of degreasers that includes natural or synthetic hydrocarbons, surfactants, corrosion inhibitors and other additives. They are also known as emulsion degreasers, since during the degreasing process the application of water is required for washing, rinsing or both. They are used in the same degreasing processes as alkaline aqueous solutions, i.e. in immersion and spraying processes.
• Chlorinated solvents: they have been widely used because of their capacity to eliminate a great variety of greases, oils, waxes, etc., and because they are not corrosive to metal, flammable or explosive. In addition, its use is of particular interest in vapor degreasing processes because the boiling point is low enough compared to oils and greases for the vapor to be a pure chlorinated hydrocarbon, but high enough for the vapor to condense easily in the cold zone, and with a higher density than air to replace air in the vapor zone.

Selection of process type and degreasing product

The selection of the degreasing process and the chemicals to be used is determined by, among other relevant factors:

• The characteristics of the oil, grease or dirt to be cleaned
• The type of metal and the morphology of the parts
• The degree of cleanliness required
• Impact on the environment
• The economic cost
• The number of parts
• The requirements of the post-treatment to be applied to the parts (painting, galvanizing, etc.).