7.3.2. After application

After application reduce the pressure with the control valve down to zero. Secure the gun and remove the nozzle. The nozzle should be thoroughly cleaned and stored separately. Then, the can with the paint is removed from the pump and replaced by a container filled with thinner/cleaner. Before circulating the thinner through the system residual paint should be discharged from the system and fed back into the paint can by increasing the pressure a little. Thereafter thinner/cleaner is circulated through the system for 5 - 10 minutes. Remove the thinner/cleaner from the system and spray out the rest of the thinner. The air valve is then closed and the pressure released by pressing the trigger again. This is followed by disconnecting and cleaning the filter. The latter is thoroughly cleaned using a spray-gun. All parts with the exception of the nozzle are subsequently reassembled. Finally, the complete equipment must be cleaned with thinner/cleaner until clean thinner is coming out. Then, increase the pressure up to approximately 5 kg/cm², secure the spray gun and disconnect the air supply.

When the spray equipment is not in use it should always be filled with thinner or cleaner, from the ball valve at the bottom of the paint pump and to the valve in the spray gun. It should be stored like this until next time it is used. The high pressure hose and spray gun should never be dismantled when the spraying equipment is put away. The equipment will thus always be ready for use.

7.4. Application and curing conditions

All paints are affected by the environmental conditions during the painting work as well as the conditions during drying / curing of the paint. Unfavourable conditions can lead to a number of failures. Below the most common failures are listed.

Temperature.

• Temperature affects the drying / curing process and rate of evaporation of solvents.

• The temperature of steel and air influence the rate of evaporation of the solvent from the coating and also the rate of curing. Too low a temperature reduces the speed of curing. In some cases the curing stops completely.

• Skinning may occur when paint is applied to a cold surface and is directly exposed to the sun or other source of heat.

• The recoating times for individual coats of the systems are influenced by steel and air temperature.

• Paint applied at temperatures outside the limits indicated may not adhere, dry or cure satisfactorily, and their performance may be impaired.

• The best result is obtained when the surface to be coated is warmer than the ambient air temperature.

• Too high a substrate temperature will promote pin-holes.

Humidity

• Humidity also affects drying time. When humidity is high, i.e. > 85 %, solvents evaporate more slowly, and drying time is longer.

• Painting at a humidity above 85 % is not recommended.

• The dew point is the temperature at which the air deposits humidity on a surface. Before paint is applied and during application, the temperature of the steel surface should be at least 3 ^oC above the dew point.

• Finished coated tanks must be kept in a condensation-free condition until the coatings have cured sufficiently to withstand condensation.