Can You Identify RoHS-Compliant Fasteners by Colour?

Whether a fastener meets RoHS has to be checked for both the base material and the surface finish; a base material such as leaded free-cutting steel can itself contain a restricted substance. For fasteners, the most common issue is the hexavalent chromium (Cr⁶⁺) used in chromate conversion coatings after zinc plating. It was widely used for decades because it is cheap and corrosion resistant, so products that need RoHS compliance should have their restricted substance content confirmed and a suitable alternative treatment considered.

The ten restricted substances

The four plasticisers were added by the RoHS 2 amendment (EU 2015/863, informally "RoHS 3") and apply from 22 July 2019 (July 2021 for medical and monitoring/control equipment). Limits are 0.1% in homogeneous materials (cadmium 0.01%). A bolt on its own is not electrical equipment; RoHS applies when it is built into one.

Can you tell by colour? Only partly

The short answer is that you must judge by the finish material and its composition, not by colour. There are useful tendencies, however.

The table below is a reference to the likelihood of RoHS compliance for common finishes. Final compliance must be confirmed from the actual composition of the material and coating, test data and the customer's requirements.

Note that the table contains two pairs that look identical but sit on opposite sides. Clear and black chromate exist in both hexavalent and trivalent form and cannot realistically be told apart by eye, and Dacromet and Geomet are both silver-grey. These are the clearest demonstration that colour is not a criterion. "Dacromet" is often used loosely on site as a generic term for zinc flake coatings, so check the exact process name on the specification and which chromate (hexavalent or trivalent) it uses.

Trivalent yellow chromate also exists as a replacement for hexavalent yellow, so a yellow part may well be compliant. ISO 19598, which covers Cr(VI)-free treatments, also allows appearances ranging from colourless to coloured and iridescent. Whatever the colour, appearance is only an indication — confirm from the process specification and compositional analysis.

Changing the finish changes not only corrosion resistance but also friction, so the same torque can give a different preload. When switching to a RoHS-compliant finish, re-check the tightening torque (tightening torque and friction).

There is no mandatory "RoHS certificate"

RoHS does not require a third-party certificate issued by a body designated by the EU. The manufacturer of the finished electrical or electronic product assesses conformity and keeps the EU Declaration of Conformity (DoC) and technical documentation (EN IEC 63000:2018 is used for the technical documentation). Supplied components such as bolts provide supporting evidence on request — composition test reports for the material and finish, or a supplier's declaration of conformity.

For fasteners made only of a metal base and inorganic plating, with no organic coating, the four heavy metals (Pb, Hg, Cd, Cr⁶⁺) are generally checked first. Where other materials are added — organic sealers, lubricant coatings, nylon patches, SEMS with resin washers — PBB, PBDE and the phthalates may also need to be reviewed. The final scope depends on the product's construction and the customer's requirements.

For hexavalent chromium the test method matters too. IEC 62321-7-1, used for Cr(VI) in coatings on metals, makes a qualitative judgement of whether Cr(VI) is present; it should not be read as a simple comparison of concentration with 0.1%. When reading a report, check the Cr(VI) result together with the test standard applied and the verdict (not detected, detected, inconclusive, etc.).

※ Nickel plating is not restricted under RoHS. However, products sold in Europe that stay in prolonged contact with skin may be subject to the separate REACH restriction on nickel release, which should be checked.