With recent changes to the RoHS regulations (Restriction of Hazardous Substances) for the European Union (EU) Market, we have had some inquiries from our customers about compliance with RoHS for machined parts and subassemblies. The regulations limit the use of ten substances:
- Lead (Pb)
- Mercury (Hg)
- Cadmium (Cd)
- Hexavelent chromium (Cr6+)
- PBB, PBDE, DEHP, BBP, DBP, and DIBP
These substances are limited to 0.1% by weight, except cadmium with a limit of 0.01%. Certain exemptions to these basic limits apply for specific applications. Of most interest to machined parts are the special limits for lead in certain metal alloys. Steel is permitted up to 0.35% lead for machining purposes and in galvanized steel. Aluminum alloys can have up to 0.4% lead by weight. Copper alloys are allowed 4% lead. Other exemptions apply for lighting and glass.
With machined parts, the two most likely causes of non-compliance with RoHS are surface finishes (plating, anodizing, etc.) utilizing hexavalent chromium or cadmium, or alloys with lead above the permitted level. While many steel and stainless steel alloys contain chromium, that chromium is not in the hexavalent state and is not an issue for RoHS compliance.
Surface Finishes for RoHS Compliance
While cadmium or chrome plating may be obvious sources of non-compliance with RoHS requirements, many other surface finishes use hexavalent chromium especially those performed using older specifications. For example, the gold in gold chemical film (“chem film”) treatments comes from application of hexavalent chromium. MIL-DTL-5541 provides specification for RoHS compliant chem film treatment, although the treatment will provide clearer coating.
Surface treatment specifications to avoid:
- Chrome plating: all specifications including QQ-C-320, AMS-2460, AMS 2406, AMS 2438, ASTM B-177
- Cadmium plating: all specifications including QQ-P-416, AMS-2400, AMS-2401, AMS-2419, AMS-2451/4, AMS-C-8837, ASTM B766, ASTM F519, MIL-STD-865, MIL-STD-870, MIL-STD-1500, MIL-STD-1501
- Chem film: MIL-C-5541, MIL-DTL-5541 Type I
- Anodize: MIL-A-8625 Type I
Instead, try specifying these standards:
- Chem film: MIL-DTL-5541 Type II (or ASTM B921)
- Anodize: MIL-A-8625 Type II (sulfuric acid anodize), MIL-A-8625 Type III (hard anodize)
- Alternatives to cadmium plating (avoid hexavalent chromium post-treatments and confirm RoHS compliance): Zinc Nickel (AMS-2417 [avoid Type 2 Grade A] or ASTM B481), Aluminum Ion Vapor Deposition (AMS-2427)
The most common aluminum alloys do not contain any added lead. This includes common aerospace and commercial aluminum alloys such as 6061, 7075, 2024, 6063, 3003, 5052, 5083, 5086. Nonetheless, there are some aluminum alloys to avoid for RoHS compliance due to their lead concentrations; 2011 and 6262 aluminum are most common aluminum alloys with lead in excess of RoHS standards, although there are other alloys with added lead especially in the 2000 series of alloys.
Stainless steel alloys do not contain any lead and should provide for RoHS compliant parts as long as they are not subjected to non-RoHS compliant surface finish.
Many common brass alloys stay below the 4% lead limit for copper alloys such as C360 brass; however, any applications requiring RoHS compliance should identify specific brass alloy(s) with minimal lead.