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DELPHI DX551300 Document Information:
Title
CORROSION PROTECTIVE COATINGS – ZINC ALLOY PLATING (HEXAVALENT CHROMIUM FREE)
Delphi Automotive Systems
Publication Date:
Jul 1, 2008
Scope:
This specification covers the basic requirements for a barrel or
rack electrodeposited zinc alloy plating system over a ferrous
substrate. A plating system consists of; zinc alloy plating, a
zinc-alloy surface treatment (e.g. trivalent chromium conversion
coating), and may include a post treatment. All zinc alloy surface
treatments and post treatments must be hexavalent chromium free.
Four alloy platings are covered by this specification: zinc-cobalt,
zinc-nickel, zinc-iron and zinc-cobalt-iron. Zinc alloy plating is
especially suitable for small to medium ferrous parts such as
castings, fasteners, stampings, clips and other parts where levels
of corrosion protection exceeding pure zinc are required. Table 1
lists the zinc alloy finishes covered by this specification and
their alloy concentration limits and % nominal.
NOTE: This finish is not recommended for applications where
white corrosion is a cosmetic concern.
The specification number shown in the title is a generic number
for the different zinc alloy plating finishes. Table 2 shows the
specification numbers to be used on the drawings and reflects the
basic requirements of the specification.
Drawing call out example: DX551302 per DX551300.
This example from Table 2 indicates a zinc-iron plating with a 8
micrometer minimum thickness that has a zinc alloy surface
treatment. The coating must withstand a minimum of 600 hours
neutral salt spray without evidence of base metal corrosion (red
rust). A general topcoat is added to enhance the corrosion
resistance. The presence of a suffix after the specification number
(example: DX551302-F) indicates an approved source supplemental
qualification requirement, as described in Section 11.
Specific requirements shown on the part drawing shall take
precedence over any requirements in this specification, or may be
in addition to the requirements of this specification.
Some colors are typically obtained by the use of specific zinc
alloy surface treatments, post-treatments or color dyes.
The use of zinc alloy plating and related finishes described in
this specification on threaded surfaces and/or bearing surfaces of
joints could affect the torque-tension relationship. It is
recommended that a torque-tension study of the fastener joint be
performed before releasing the specified plating and finishes for
use on new threaded applications. See Table 1 of this
specification.
Zinc alloy plated parts or their corrosion products must not
come in contact with stressed Polyamides 6 or 66.
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