1.1 Significance of pretreatment: The general pretreatment engineering process is grinding, preparation, washing, washing, electrolysis, deesterification, washing, acid leaching and activated water, neutralization, washing, and electroplating.
1.2 Purpose of pre-treatment: The purpose of pre-treatment is to obtain a good coating, because the plating parts will have grease, oxide scale, hydroxide, dust and other dirt attached to the plating parts during the manufacturing, processing, handling, and storage. On the surface, if these contaminants are not removed and electroplating is performed, a good plating layer will not be obtained. The quality of plated parts, pre-treatment occupies an important position.
1.3 Plating defects caused by poor pretreatment:
The coating defects caused by poor pretreatment include the following items: (1) peeling, (2) swelling, (3) stains, (4) uneven gloss, (5) unevenness, (7) small holes (8) ) Reduce corrosion resistance, (9) Embrittlement. Poor electroplating is a major cause of pre-treatment.
1.4 Methods for removing oxides and rust: The basic methods are: 1. Sandblasting and rust removal 2. Drum rust removal, 3. Brushing and rust removal, 4. Acid dipping, 5. Salt bath rust removal, 6. Alkali agent removal Rust, 7. Pickling.
1.5 Purification methods: The purification methods are: 1. Alkali agent washing, 2. Solvent washing, 3. Emulsification washing, 4. Electrolytic alkaline washing, 5. Acid washing, 6. Steam degreasing, 7. Spraying Sand washing, 8. Drum washing, 9. Brush washing, 10. Acid dipping, 11. Electrolytic acid leaching, 12. Salt bath rust removal, 13. Alkaline rust removal, 14. Ultrasonic washing, 15. To remove paint, 16. Bead strike method.
1.6 The principle and advantages of ultrasonic cleaning: Principle: The function of ultrasonic cleaning is to conduct in the liquid by the fluctuations above the sound frequency of human hearing. When the sound wave is conducted in the detergent, because the sound wave is a longitudinal wave, longitudinal wave The action of the pushing medium will cause the pressure in the liquid to change and produce countless tiny vacuum bubbles, which is called the
1.7 abrasive blast cleaning:
It sprays abrasive particles on the surface of the workpiece in a dry or liquid manner to remove dirt, scale, etc. for conditjoning the surface for further processing. It is mainly used for: (1) Remove dust, rust, frosted, or paint (2) Roughen the surface for paint and other coating treatments
(3) Removal of burrs (4) Matte surface treatment (5) Removal of residual material (flash) (6) Glass or ceramic etching, other methods can be divided into dry blast cleaning and Wet blast cleaning
1.8 Abrasive materials for dry blast cleaning
The abrasive materials used are:
1. Metallic grit 2. Metallic shot 3. Sand 4. Glass 5. Agricultural products such as walnut husk, rice husk, wood chips
Mainly used for: (1) Removal of burrs from precision workpieces (2) Matte surface treatment (3) Inspection of ground and hardened workpieces (4) Removal of tool marks on hard workpieces ( 5) Remove slight scale (6) Remove oxides from electronic parts and printed circuit boards for soldering (7) Remove welding scale.
1.9 Wet jet grinding and cleaning abrasive materials (Abrasives):
There are many types and sizes of abrasive materials used, ranging from 20-mesh to 500-mesh. The abrasive materials include: 1. Organic or agricultural products, such as walnuts, 2. Inorganic materials such as sand, quartz, alumina, etc.
1.10 Electrolytic grinding: Electrolytic grinding is similar to electroplating, which requires direct current. Electrolyte, but the work is placed on the anode. The current concentration of the protruding metal part and the greater polarization of the recess are used to smooth and polish the workpiece, and also make the surface Passivation is more wear-resistant. Electrolytic grinding removes a small amount of metal surface, deeper marks and non-metallic impurities cannot be removed. Electrolytic grinding is better than mechanical grinding in that there is no deformation, no brush marks, and no directionality. And can show the true metal color.
1.11 Forms of buffing: (1) hard buffing (2) color buffing (3) contact buffing
(4) Polishing wheel polishing Mush buffing.
The polishing wheel is cut into a round shape with velvet felt or soft tanned leather, and the number of plates is overlapped and stitched into a wheel, and the surface is covered with abrasives such as corundum powder, diamond grit, iron oxide, chromium oxide, etc., use this To grind is the polishing wheel processing.
Barrel finishing:
Mix castings, punching products and other small parts with metal scraps and abrasive materials, put them in a rotating drum, and after a long time of rotation, they can be hammered and ground due to collisions and frictions, etc., and can be used for dehorning , Polishing, surface cutting, etc.
