ECOLOGICAL PREPAINT TREATMENT OF ALUMINIUM ... - Aluplanet

CFP alloy variation
Neutral salt spray at 4000 hour exposure
Type
A1
B1
C1
Alloy
Al 6061
Al 5052
Al 2024
Paint type
Polyester
Interpon
D1036
Polyest er
Interpon
D1 036
Polyester
Interpon
D1036
Paint
thickness
Nominal 70 microns
Creep back
mm
0
0
0
Rating
ASTM 1654
10
10
10
Slide 12: alloy variation
Enhanced Process
To achieve optimum paint performance on aluminium alloys, quality assure in-service
reliability and meet the needs of demanding corrosive environments, a more extensive
prepaint treatment prior to CFP has found to be beneficial, as outlined on slide 13.
The enhanced sequence starts with a non-etch BioChemical alkaline cleaner as the preferred
choice for surface oil removal, followed by water rinsing. This is shown on the slide optimized
with the use of a BioFilter to extend performance and solution life, which is available to
applicators as an option. Etching is then required to active the surface. Experience has shown
that an acidic etch produces a more uniform substrate profile which is highly compatible with
passivation.
After etching, surface smuts may be generated which tend to be heavier the more highly
alloyed the substrate type, smuts are particularly heavy on copper based alloys. They mainly
consist of oxides and intermetallics which are readily removed by a suitably formulated acid
treatment. Following smut removal, double water rinsing is recommended prior to passivation.
Some instances have found that final finish improvements can be realized when using
deionized water in the second stage rinse, but it is always recommended to use deionized
water after passivation. This process route can be used effectively for both spray and
immersion, and for both wrought and cast aluminium alloys.
Enhanced Process
Spray Zones
BioChemical
Clean
Water Rinse
Acidic Etch
Water Rinse
Desmutt
Water Rinse
Chromium-free
passivation
Slide 13: enhanced prepaint process