Next to proper surface preparation, application is the most important item in obtaining optimum coating performance. Even the best-formulated paint will not
perform in an outstanding manner unless it is properly applied.
The following are general conditions affecting most coating applications:
||The optimum temperature range for coatings application
is 60° F (15°C) to 90° F (32° C). Coatings generally should not be applied
if atmospheric or substrate temperatures are below 40°F (4° C) or above
100° F (43° C) at the time of application. Surface temperatures above 90°
F (32° C) may cause the film to dry too rapidly, resulting in pinholes or
holidays. Surface temperature below 40° F (4° C) for single package products,
or 50° F (10° C) for most activated products may cause slow or incomplete
Coatings should not be applied unless the temperature
of the surface being coated is, and remains, at least 5° F (2.7° C) above
the dew point, otherwise condensation may occur on the surface and impair
adhesion or appearance. Slow drying materials, spray applied, do not have
much effect on substrate temperature. However, quick-drying coatings containing
fast-drying solvents may reduce the surface temperature considerably.
Humidity may also affect the drying time of coatings.
High humidity lengthens the drying time for coatings that “cure” by solvent
or water evaporation. The drying time for most chemically cured coatings
will be relatively unaffected, except for the drying time for inorganic
zinc, or other moisture cured coatings.
|| Coatings should not be applied outdoors when winds are
excessive. Dry overspray on the paint film and overspray contamination of
adjacent areas may result.
Coatings should not be applied outdoors when any form
of precipitation is present or imminent. Precipitation may:
- Cause poor adhesion
- Wash off freshly applied coatings
- Deposit chemical contamination
- Cause unsightly spotting
- Cause poor film properties
Application instructions printed on coating containers
shall be followed. Sharp edges and corners should be spot primed prior
to application of the regular prime coat. Alternate colors from coat to
coat can be used as a visual check where practical. This guide coat practice
helps to insure complete coverage of each coat.
Where exposure conditions are severe, it is advisable
to check for pinholes and holidays and recoat them promptly. Skips, holidays
and pinholes can be detected by using a low voltage wet sponge holiday
In most cases, coatings can be applied by alternative means. The method of application selected will depend on the following factors:
- Type of coating
- Size and configuration of paintable item
- Applicator skill level
- Equipment availability
- Plant and process area restrictions
- Work code limitations
- Economics (productivity, material costs, etc.)
For your guidance, the application method comparison chart below summarizes the major advantages and disadvantages of some of the more common application
methods, and indicates the estimated coverage per day using each method.
||Estimated Coverage Per Day in Square Feet
|| 1. Convenient for touching up small areas.
2. Low skill level required.
|1. Expensive and time consuming.
2. Non-uniform film thickness.
3. High film builds require multiple coats.
||1. Provides greater productivity than brush for large surface
areas where spray methods are restricted.
2. Low skill level required.
|1. More time consuming than spraying.
2. High film builds generally require multiple coats.
3. Uniform film thickness more difficult to achieve than with spray
|| 1. Greatly reduces overspray (or rebound) experienced
with a conventional spray system.
2. Gives painter the ability to apply heavy coatings in a single pass.
3. Coatings often need not be thinned for application when airless equipment
| 1. Should not be used for fine work.
2. Spray pattern edges are not sufficiently feathered as is the case with
air atomization patterns.
|| 1. Significantly increases transfer efficiency of coatings
versus either conventional spray or airless spray.
2. Provides excellent control of sprayed coating application.
3. Allows for wide versatility with rates of application. (i.e. from very
slow to moderately fast.)
4. Reduces preparation and masking time needed in the work area.
5. Provides for a safer, cleaner work environment for the applicator.
6. Allows the attainment of very smooth finishes.
| 1. Some restriction due to viscosity limitations.
2. There is an upper limit to application rate, particularly with high viscosity
3. Requires a higher skill level than airless but no more than conventional
|| 1. Provides the ultimate in coating transfer efficiency.
2. Requires the least work area masking.
3. Allows for sprayed coatings to cover hard to reach, odd size items with
the least effort.
4. Provides the cleanest work environment for the applicator.
5. Available in conventional spray, airless, and HVLP spray technology versions.
| 1. High degree of complexity.
2. Requires that several coating and substrate variables be determined and
fall within specific limits for full results to be achieved.
3. High cost of equipment.