28-11-2012, 06:15 PM
SURFACE TREATMENT
[attachment=41587]
Introduction
Good surface preparation is the key to obtain good protection by surface coating
Method of surface preparation depends on
Nature of substrate
Type of contamination
Type of coating
Surface preparation is done for removal of various contaminants present on the surface of substrate
Type of substrate
1- Metallic
Ferrous
Non Ferrous
2- Non Metallic
B. Chemical Pretreatment
B.1 Solvent Degreasing
For removal of oil and grease from the surface
Articles are suspended in the vapour of boiling solvent. Condensation will take place as long as the temperature of article is below that of the vapour
B.2 Alkaline Cleaning
For removal of soil and grease from the surface
Hot alkali salts such as hydroxide and carbonate which enables the soil and grease to saponify and thereby convert them to water soluble soaps
SURFACE TREATMENT FOR MAGNESIUM
The surface can be given one of the following pre treatment
Acid Chromate
Phosphoric Acid Wash
Etch Primer
Surface treatment for polymer and plastics
Primers based on the chlorinated poly olefins are often used as adhesion promoters.
Oxidizing agents such as chromic acid, sulphuric acid are used to provide polar groups
Surface can be oxidized by flame treatment directly .
Spray of solution of benzophenol is used to generate the free radical that initiates auto oxidation of the surface.
[attachment=41587]
Introduction
Good surface preparation is the key to obtain good protection by surface coating
Method of surface preparation depends on
Nature of substrate
Type of contamination
Type of coating
Surface preparation is done for removal of various contaminants present on the surface of substrate
Type of substrate
1- Metallic
Ferrous
Non Ferrous
2- Non Metallic
B. Chemical Pretreatment
B.1 Solvent Degreasing
For removal of oil and grease from the surface
Articles are suspended in the vapour of boiling solvent. Condensation will take place as long as the temperature of article is below that of the vapour
B.2 Alkaline Cleaning
For removal of soil and grease from the surface
Hot alkali salts such as hydroxide and carbonate which enables the soil and grease to saponify and thereby convert them to water soluble soaps
SURFACE TREATMENT FOR MAGNESIUM
The surface can be given one of the following pre treatment
Acid Chromate
Phosphoric Acid Wash
Etch Primer
Surface treatment for polymer and plastics
Primers based on the chlorinated poly olefins are often used as adhesion promoters.
Oxidizing agents such as chromic acid, sulphuric acid are used to provide polar groups
Surface can be oxidized by flame treatment directly .
Spray of solution of benzophenol is used to generate the free radical that initiates auto oxidation of the surface.