Hamilton Jet HJ212, Installation And Service Manual

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Installation and Service Manual
Maintenance
Bare metal refurbishment - aluminium
The aluminium castings used in the manufacture of Hamilton jets require special attention when the coating
has been damaged down to bare metal. The surface needs to be very clean and freshly abraded prior to the
application of a suitable primer coating to ensure a good bond is achieved. Masking of the impeller and
mainshaft is optional as it is acceptable to have overspray on the mainshaft and impeller.
The area of refurbishment and immediate surroundings should be degreased with a water soluble degreaser
and thoroughly rinsed off with clean water. The area should be sanded back to fresh bare metal with 80 to
120 grit aluminium oxide abrasive paper or sanding disc feathering the edges until a smooth surface is
achieved. The affected area may be lightly sweep blast cleaned using non-metallic blast media. Appropriate
masking is required to ensure that pushrods, bearings and seals are not blasted and that blast media does
not contaminate bearings, bushes, and seals.
Heavy or medium abrasive sweep blasting of aluminium castings will cause excessive
material loss from the casting.
The surface should then be blown down or washed to remove sanding debris followed by a solvent wash to
leave the surface dry and clean. For parts finished with the grey gloss scheme, mask the remaining paint as
applying epoxy primer over the gloss finish is not recommended. Within 30 minutes of abrading the
aluminium surface, a coat of aluminium surface primer (epoxy primer or zinc chromate etch primer) should
be applied to seal the exposed aluminium surface.
It is extremely important to apply the first paint coating within 30 minutes of abrading the
bare aluminium in order to achieve the optimum paint adhesion and therefore paint life.
The use of a zinc chromate etch primer will provide optimum paint system performance in terms of corrosion
protection. Etch primer must only be applied to bare metal, and the coating should be very thin as 'thick'
layers of etch primer lack peel strength - refer to the manufacturer’s specifications and recommendations for
application.
The next step is to apply the epoxy primer. Two coats of epoxy primer are generally required to achieve an
adequate paint dry film thickness.
If filling is required to repair the metal surface, apply a suitable marine epoxy filler. The filler should be
applied after application of the epoxy primer. Sand the filler to achieve a smooth surface and then apply a
further coat of epoxy primer over the filler.
Finally, apply the appropriate top coats to the primed surfaces.
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