The process is
characterized by applying three successive coating layers
on external steel surface after cleaning it to the SA
2.5 grade of Swedish standard SIS 055900.
The first layer is a fusion-bonded epoxy powder (150
micron/0.150mm thick) by electrostatic spraying guns
on heated surface to a minimum of 190 degrees centigrade
or as recommended by the powder manufacturer.
The second layer is adhesive (200 micron/0.20mm) which
is applied by lateral extrusion over the epoxy layer
when the epoxy powder is still in the polymerization
phase at a temperature of 210-230 degrees centigrade.
The third layer of polyethylene (2200 micron/2.2mm)
is applied by lateral extrusion on the adhesive layer
at a temperature of 230-270 degrees centigrade and is
adjusted according to the requirement. The pressure
roller is used to prevent air entrapment in the PE layer.