Cadmium Substitution - garteur

GARTEUR LIMITED
A.2.4
Delta-tone/Delta seal
Coatings were applied by Ewald Dörken AG but detailed information about the process is
not available. The complete protective scheme, Delta-Magni, consists of two coatings; a
thin layer containing zinc flakes known as Delta-Tone and an organic coating
incorporating a lubricant and marketed as Delta-Seal. Literature produced by the
company indicates that the coatings are applied by dip-spin, dip drain or spray. After
application the Delta-Tone coating is cured at a temperature of approximately 200 o C. To
increase the corrosion resistance of the coating and improve the frictional properties a
coating of Delta-Seal is applied. This is an organic topcoat, which contains a lubricant
and is also cured at relatively low temperatures.
A.2.5
Electrodeposited aluminium
The electrodeposition of aluminium by the Galvano-Aluminium process is carried out in
an organic bath consisting of aluminium-alkyl complex solutions. The process allows
aluminium to be deposited directly onto a steel substrate unlike earlier processes which
required the use of a copper or nickel intermediate layer. The various stages in the
plating process are detailed in table A8.
The bath parameters employed are given in table A9.
A.2.6
PVD aluminium coatings
Aluminium coated panels and fasteners prepared by physical vapour deposition were
supplied by Aerocoat. The deposition process was carried out in accordance with
Defence Standard 03-28(Part 1). Details of the procedure used are given in table A10.
A.2.7
Unbalanced magnetron sputtered aluminium - magnesium coatings
Aluminium - magnesium coatings were deposited using an unbalanced magnetron
sputtering technique operated at Salford University. The test panels were initially
degreased using an ultrasonic bath containing alcohol and then placed in the vacuum
chamber. The magnetron sputtering chamber was evacuated to 10 -5 Torr or below and
then backfilled with high purity argon to a pressure of around 5x10 -3 Torr. The chamber
contained two consumable targets, one commercial grade aluminium (99.4% purity) and
one of commercial grade magnesium (99.5% purity) Prior to deposition, the steel test
panels were sputter cleaned, typically at an applied voltage of 1 kV for 30minutes to
remove any traces of surface contamination.
Following this high voltage sputter cleaning process, a low-voltage was applied to the
test panels, typically -50V (DC) to provide an external bias during deposition. The targets
were energised using an electrical current to typical power levels of 3kW for an
aluminium target and 1.5 kW for magnesium target. The coating process was continued
for a sufficient time to allow the required thickness of deposit to build up on the
substrates. After the desired thickness had been obtained, the deposition process was
halted and the coupons allowed to cool under vacuum to prevent oxidation. A typical
deposition rate was 0.3μm min -1 . Further information on the unbalanced magnetron
sputtering of aluminium - magnesium coatings is given in references A2 and A3.
A.2.8
Electrodeposited cadmium coatings
Panels and fasteners were coated using a standard cyanide electroplating bath operated
in accordance with Defence Standard 03-19 [A4].
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GARTEUR SM/AG17 TP128