Department of Defense Issues Final Procurement Rule on Minimizing the Use of Materials Containing Hexavalent Chromium
The U.S. Department of Defense in early May issued its final procurement rule governing military uses of hexavalent chromium. During the multi-year review of the issue, NASF technical and policy committees provided input to inform the Pentagon’s decision.
What does the rule cover and what is exempt?
The rule only covers hexavalent chromium-containing materials that remain on or in the component. It does not cover processes that use hexavalent chromium solutions, if they do not leave hexavalent chromium in the coating. In addition, the rule uses the familiar definition of a homogeneous material, which is explicitly defined to include coatings, but is meant to exclude heat treatments and other surface modifications, which are considered to be part of the bulk material.
Conversion coatings are explicitly exempt, because they are intrinsically inhomogeneous, whether on aluminum and magnesium alloys, or on coatings such as Zn, Cd and anodize.
Consequently it has no effect on:
- Conversion coating and chromate converted coatings
- Hard chromium plating
- Chromic acid anodizing
- Chromate washes, etches, pickling and stripping solutions, etc.
- Low chromate metallic ceramics (<0.1% Cr6+)
- Chromium diffusion heat treats (such as chromizing and some carbonitriding processes)
The rule applies only to coatings left on the surface that contain >0.1% chromate. The primary materials used by DoD that fall into this category are:
- Chromated primers (for aircraft skins and components)
- Aircraft fuel tank internal coatings
- Wet install fastener sealants (used on Naval aircraft)
- Other chromated sealants (used to seal panels, covers, electronics, etc.)
- Chromated metallic-ceramic paints containing >0.1% Cr6+ (MIL-C-81751, used in turbine engines)
What is the impact?
In order to provide a phase-in period, the rule does not apply to any weapons system that has passed Milestone A, which is a very early milestone. It does not therefore apply to new systems such as the F-35 fighter or the current MRAP vehicles. However, DoD is encouraged to reconsider the use of chromated products during major modifications or follow-on procurements. This means that, even with existing systems, contracts for a new procurement (an additional number of F-18's or MRAPs, for example) could preclude the use of chromated coatings.
However, nothing in this rule precludes any weapon system from eliminating hexavalent chromium on their own account. MRAP suppliers, for example, are required to use e-coating or direct-to-metal painting without a chromate wash, while F-35 suppliers must use non-chromium primer. The intent of the rule is to change the default from chromate to non-chromate; as a result we are likely to see more contracts, including contracts for replacement components, stipulating the use of hexavalent chromium-free materials, whether or not they are required by the DFARS.
Reference and Copy of Final DFARS Rule:
Federal Register Volume 76, Number 87, Pages 25569-25576 (Thursday, May 5, 2011)