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Fundamentals of Corrosion
7.7.3.3 Force Drying
The cure rate of many thermoplastic and thermosetting coatings can be
accelerated by exposure to elevated temperatures that are below those considered as baking temperatures.
7.7.3.4 Reflowing
Certain thermoplastic coating films will soften and flow, becoming smooth
and glossy at elevated temperatures. The automotive industry uses this technique on acrylic lacquers to eliminate buffing.
7.7.3.5 Radiation Curing
Bombardment with ultraviolet and electron-beam radiation with little
increase in temperature will form and cure films. However, infrared radiation increases the surface temperature and it therefore is considered a baking process.
7.7.3.6 Vapor Curing
This method is used for two-component coatings. The substrate is coated
with one component of the coating in the conventional manner. It is then
placed in an enclosure filled with the other component — a curing agent in
vapor form — where the catalysis or crosslinking conversion takes place.
7.7.4 inspection
The most important part of a coating operation is to guarantee that the coating has been properly applied. It is better to have a less effective coating
applied properly than the best coating applied poorly.
There are a wide variety of aids, standards, and inspection instruments
available to check the quality of the coating system. These include devices
for checking the cleanliness of a prepared surface, the depth of a blastcleaning anchor pattern or profile, and various magnetic, eddy current, and
nondestructive thickness gauges (capable of measuring the total thickness
or the thickness of each coat in a multicoat system). In addition, there are
instruments available to monitor temperature, humidity, and dew point on
a continuous basis.
After application, adhesion tests and holiday tests (for pinholes and other
discontinuities) can also be specified.
It is also important to realize that even if properly applied, the coating
does not last forever. During the first 6 to 12 months after application, visual
inspection will be able to detect inadvertent misses, thin spots, or weak areas
in the coating. Repair, if required, should be done at this time.
Fundamentals of Corrosion
7.7.3.3 Force Drying
The cure rate of many thermoplastic and thermosetting coatings can be
accelerated by exposure to elevated temperatures that are below those considered as baking temperatures.
7.7.3.4 Reflowing
Certain thermoplastic coating films will soften and flow, becoming smooth
and glossy at elevated temperatures. The automotive industry uses this technique on acrylic lacquers to eliminate buffing.
7.7.3.5 Radiation Curing
Bombardment with ultraviolet and electron-beam radiation with little
increase in temperature will form and cure films. However, infrared radiation increases the surface temperature and it therefore is considered a baking process.
7.7.3.6 Vapor Curing
This method is used for two-component coatings. The substrate is coated
with one component of the coating in the conventional manner. It is then
placed in an enclosure filled with the other component — a curing agent in
vapor form — where the catalysis or crosslinking conversion takes place.
7.7.4 inspection
The most important part of a coating operation is to guarantee that the coating has been properly applied. It is better to have a less effective coating
applied properly than the best coating applied poorly.
There are a wide variety of aids, standards, and inspection instruments
available to check the quality of the coating system. These include devices
for checking the cleanliness of a prepared surface, the depth of a blastcleaning anchor pattern or profile, and various magnetic, eddy current, and
nondestructive thickness gauges (capable of measuring the total thickness
or the thickness of each coat in a multicoat system). In addition, there are
instruments available to monitor temperature, humidity, and dew point on
a continuous basis.
After application, adhesion tests and holiday tests (for pinholes and other
discontinuities) can also be specified.
It is also important to realize that even if properly applied, the coating
does not last forever. During the first 6 to 12 months after application, visual
inspection will be able to detect inadvertent misses, thin spots, or weak areas
in the coating. Repair, if required, should be done at this time.