3. The type of paint
4. The shape and size of the object to be painted
5. The period of application process
6. Cost
7.13.3.1 Brushing
This was once the main coating method, but at the present time,s pray
coating is more widely used. Brush coating has the following advantages:
1. Applicators are simple and inexpensive.
2. Complicated forms and shapesc an be coated.
3. Thick films are obtained with one coat.
4. It provides particularly useful antirusting coating.
The disadvantage of brushing results from the nonuniformity of coating
layers, especially coating layerso frapidly drying paints.
7.13.3.2 Spray
There are two types of spray coatings: air sprays and airless sprays. These
coatings ares ubdividedi nto hot and cold types.
7.13.3.2.1 Air Spray
Air spray is ap rocess for spraying fine paint particles atomized by compressed air.D ryingr ates are higha nd au niform and decorative surfacei s
obtained. This method is used with paints that are not suitable for brushing
methods, for mass produced painted products, or for products where
surfacea ppearance is important.
7.13.3.2.2 Airless Spray
In an airless spray system,h igh pressurei ss upplied to the paintt hat is
forced through ah ighp ressurer esistant hose and airless spray gun. High
viscosity paints are warmedb efore spraying. Thist echnique has the
following advantages over the air spray system:
1. The sticking ratio of paint is increased to 25–40%.
2. Thicker films can be applied.
3. The running of paint on the object is reduced.
Steel structures andb ridge girders can be coated in the factory by this
method because the efficiency of work is several timesh igher than brushing. However, its paintl oss is 30–40% greater than for paints applied
by brushing.
Corrosion of Linings and Coatings
472
CAT8247—CHAPTER 7—17/10/2006—15:04—TRGANESH—XMLM ODEL B–pp. 403–485
4. The shape and size of the object to be painted
5. The period of application process
6. Cost
7.13.3.1 Brushing
This was once the main coating method, but at the present time,s pray
coating is more widely used. Brush coating has the following advantages:
1. Applicators are simple and inexpensive.
2. Complicated forms and shapesc an be coated.
3. Thick films are obtained with one coat.
4. It provides particularly useful antirusting coating.
The disadvantage of brushing results from the nonuniformity of coating
layers, especially coating layerso frapidly drying paints.
7.13.3.2 Spray
There are two types of spray coatings: air sprays and airless sprays. These
coatings ares ubdividedi nto hot and cold types.
7.13.3.2.1 Air Spray
Air spray is ap rocess for spraying fine paint particles atomized by compressed air.D ryingr ates are higha nd au niform and decorative surfacei s
obtained. This method is used with paints that are not suitable for brushing
methods, for mass produced painted products, or for products where
surfacea ppearance is important.
7.13.3.2.2 Airless Spray
In an airless spray system,h igh pressurei ss upplied to the paintt hat is
forced through ah ighp ressurer esistant hose and airless spray gun. High
viscosity paints are warmedb efore spraying. Thist echnique has the
following advantages over the air spray system:
1. The sticking ratio of paint is increased to 25–40%.
2. Thicker films can be applied.
3. The running of paint on the object is reduced.
Steel structures andb ridge girders can be coated in the factory by this
method because the efficiency of work is several timesh igher than brushing. However, its paintl oss is 30–40% greater than for paints applied
by brushing.
Corrosion of Linings and Coatings
472
CAT8247—CHAPTER 7—17/10/2006—15:04—TRGANESH—XMLM ODEL B–pp. 403–485