CASE STUDY
uring refurbishment of a UK rail bridge in winter, heavy snow, extended cold periods and a continuous flow of water from concrete above the bridge beams, made it impossible to use an ordinary coating system. Preparatory blasting work in many areas was beginning to show significant re-rusting because of the delays in coating. The contractors, with expensive scaffolding and other infrastructure in place, were anxious to avoid any further
delays and sought a solution using Alocit.
uring refurbishment of a UK rail bridge in winter, heavy snow, extended cold periods and a continuous flow of water from concrete above the bridge beams, made it impossible to use an ordinary coating system. Preparatory blasting work in many areas was beginning to show significant re-rusting because of the delays in coating. The contractors, with expensive scaffolding and other infrastructure in place, were anxious to avoid any further
delays and sought a solution using Alocit.
An area was chosen and a
test application arranged. On the day of the application, the chosen substrate was at freezing point and, although some coating was applied to this area, as it was below the
recommended minimum temperature (4°C/38°F) another, slightly warmer
substrate area was chosen
for the full test application: two on a vertical surface and one horizontal. After curing, testing showed coating thickness to be as specified and pull-off testing showed glue-line separation at 500, 750 and 900 psi. Testing to the coating on the freezing
substrate also gave a reading of 900 psi before the glue holding the dolly to the paint surface gave way.
A very surface-tolerant coating, Alocit can be applied to areas with a certain amount of re-rusting. However, in this case because of the poor condition of the substrate, the surfaces were pressure washed before application. Some areas were so badly affected that they had to be flash-blasted and rinsed with water before the first coat could be applied.
On the day full application was due to begin, heavy snow had fallen with ambient temperatures well below freezing (-4°C/25°F), but spraying was able to commence using an in-line heating block.
A very surface-tolerant coating, Alocit can be applied to areas with a certain amount of re-rusting. However, in this case because of the poor condition of the substrate, the surfaces were pressure washed before application. Some areas were so badly affected that they had to be flash-blasted and rinsed with water before the first coat could be applied.
On the day full application was due to begin, heavy snow had fallen with ambient temperatures well below freezing (-4°C/25°F), but spraying was able to commence using an in-line heating block.
SPECIFICATION & INSPECTION DATA
Conditions:
Outdoor, Freezing conditions
Products:
Alocit 28.96, filler
Alocit 28.95, primer
Alocit 28.15, finishing coat
Alocit 28.95, primer
Alocit 28.15, finishing coat
Paint System
Preparation Spec
Ambient Temps'
Substrate Temps'
Material Temps'
Equipment Data
Film Thickness / Adhesion Testing
Paint System
2 x 300 micron/12 mil index coating system using 28.15 Grey RAL 7004 as a base coat with 28.15 Green 14c39 (British Racing Green) as top coat, giving final DFT 0f 600 microns/24 mil. Stripe coat all edges, welds and bolted areas. An index system uses separate colours for each coat to ensure proper coverage.
Preparation Spec
Abrasive blast to SA 2.5/SP10 to give a blast profile of 90-95 microns/3.5-4 mil, rinse down with water where needed on wet areas to clean off blast dust
Ambient Temps'
Minus 5°C/23°F – 12°C/53°F
Substrate Temps'
5°C/41°F – 20°C/68°F (raised using hot air blowers
Material Temps'
In mixed form in batches of 30kgs (5 gal): 10°C/50°F to 15°C/59°F. At spray tip via heating block set at 20°C/68°F.
Equipment Data
Graco 68.1 airless spray pump fitted with 3/8 inch spray line with 1/4 inch whip end XTR Graco spray gun with 4-21 thou spray tip Graco In-line paint heater block.
Film Thickness / Adhesion Testing
Average DFT – 615 microns. Adhesion – range between 1600 psi and 2000 psi with all separations in the glue line.
