Composite aeronautics connectors meet REACH regulation

SOURIAU, like most manufacturers, uses hexavalent chromium, one of the substances listed as hazardous, in the surface treatment processes for many of its connectors. Although the European Chemicals Agency has granted provisional extensions of up to 12 years depending on the application, SOURIAU wished to anticipate this deadline on one of its major product lines.

SOURIAU's R&D has been working for several years on its composite connectors, which impacts the product and the surface treatment production lines. The first REACH-compliant connectors in the D38999 composite range have been qualified by the European (AECMA cert ) then American (DLA) certification bodies, then approved by Airbus and Boeing before gradually switching in 2019 for the main applications on civil aeronautics programs and many military aircraft programs. Since December 2019, the entire production of D38999 composite connectors is manufactured without the use of hexavalent chromium.

An increasingly important part of SOURIAU's D38999 range incorporates composite materials either with a nickel-plated finish or with no finish and is mainly intended for civil and military aeronautics applications. The advantage of the PEEK composite used (filled with carbon and glass fibres), is that it offers high mechanical performance in severe environments, is corrosion resistant and weighs less than aluminium. The challenge for SOURIAU was to find a REACH-compatible chemical solution for hexavalent chromium-free surface treatment of the connectors.

Thomas Pichot, R&D manager at SOURIAU explained: "We no longer use hexavalent chromium, which was previously needed to improve the adhesion of coatings on the composite substrate of our housings. We have developed the first innovations without hexavalent chromium for motorsport applications and now use for all of our Aerospace and Defense applications a new preparation treatment on composite which allows us to ensure the adhesion of successive metal layers equally well without needing this substance.

“This builds on the environmental approach we used for aluminum connectors, where we have also qualified hexavalent chromium-free passivation in our zinc-nickel treatment process. All substitute products developed and deployed are now certified non-hazardous and fully compliant with all the various environmental regulations, including REACH.

“While the challenges are obviously of a technical nature, the benefits are largely ecological, since this changeover has already enabled us to halve the volume of hexavalent chromium used in our SOURIAU Champagné production site.”