REACH : Authorised Chemicals and SVHC(s) Incorporated in Articles above 0.1% (w/w)

At this time, as far as we are aware, and have been notified by ECHA, our chemical suppliers,  etc., the only substances of very high concern included on Annexe XIV that we knowingly utilise in the application of coatings to our customers’ free issue components, are Strontium Chromate, Cadmium, some general solvents, lead fluoroborate and Disodium Tetraborate Decahydrate, and Sodium Tetraborate Pentahydrate. To date, these chemicals have been included on the candidate list, and in some cases are being included in Annexe XIV, with a view to only being permitted subject to an approved authorisation.

As of 21st September, 2017, Sodium Dichromate, Potassium Dichromate, Chromium Trioxide have been included on annexe XIV and can now only be used under the conditions of, and for the uses described, in a suitably approved authorisation.  In the case of the two dichromates their use in metal finishing is covered by the CCST authorisation (but only for aerospace applications for the next 7 years) and in the case of Chromium Trioxide their continued use is covered by the CTAC authorisation (7 years for aerospace and 4 years for general engineering).

Sodium/Potassium Dichromate is incorporated in low concentrations, as required by numerous aerospace specifications, and some existing defence specifications, in the following solutions :

  1. Nitric/dichromate passivates, used for steel (some alloys) and stainless steel.
  2. Brush alocrom.
  3. Cadmium passivates (both clear and chromate passivates).
  4. Dichromate seal, used for sulphuric acid and chromic acid anodising.

The good news is that, where still employed for aerospace uses, in the case of brush alocrom and any of the passivates they merely result in the chromate conversion of the surface and thus there is no sodium/potassium dichromate left on the article.  Also, in the case of the dichromate seal used in some instances after sulphuric acid anodising and chromic anodising, the very dilute potassium dichromate results in the deposition of aluminium oxydichromate. Thus, in every instance, negligible (i.e. less than 0.1% w/w) sodium/potassium dichromate should be present on the coated components.  NB: In the case of stainless steel passivation, other nitric only or citric acid passivates are permitted as alternatives for some materials.

Chromic acid is incorporated in small amounts in the deoxidiser solution currently used in our chromic acid anodising and alocroming, mainly for aerospace applications.  This is used as a pre-treatment step in these processes to strip the naturally occurring oxide film from aluminium parts and thus, in every instance, the subsequent processing should remove any residual hexavalent chrome, resulting in less than 0.1% w/w on the finished coated parts.  NB: We are also currently looking at replacing this deoxidiser with a non-chromated version approved by Airbus.

It is also obviously employed in the chromic acid anodising baths and is present also  in a Def Stan (03-12) type one, two and three brass passivate, alocrom 1200 (25-50%) and our anodising control stripper.  It is employed in very small amounts in a very dilute chromic seal (0.02%) sometimes used for thin film sulphuric acid anodising and Airbus’s TSA and a very dilute (0.05%) hot chrome rinse used when phosphating components.  It is also used in a very dilute concentration (0.25%) in the anodic etch sometimes employed in cadmium plating.  Still, in all cases, it should result in negligible (i.e. less than 0.1% w/w)chromic acid being present on any finished coated components.

In the case of chromic acid anodising what is actually deposited on to the surface of the article/component is an oxide film approximately 2 – 6 microns thick and, as such, providing they are processed correctly, negligible (i.e. less than 0.1% w/w) chromic acid should be present on the anodised components.

With regard to aerospace paints, hexavalent chrome is found in many forms in those we commonly use, including strontium chromate (now included on Annexe XIV), which is found in many aerospace primers in concentrations up to 30%.  As it is not converted during the application process it will be present in quite high levels in the cured primer coating and, depending on the structure of the article coated (surface area to volume ratio) may exceed the 0.1% w/w permitted on finished components.

Cadmium is obviously used at Ashton & Moore Ltd. in the cadmium plating of components and, as the name suggests, is plated on to the surface of the components, typically to a thickness of between 3.8 – 15 microns depending on the specification.  Thus, in some thin parts with large surface areas, it might be possible to exceed  the 0.1% w/w on finished components.

The two solvents, Methoxyethanol and Ethoxyethanol, are possibly present in some of the paints we apply.  However, due to the volatile nature, upon curing of the paints most, if not all of them, if present, should evaporate and thus, in all instances, the resultant amount on the finished article should be less than the 0.1% w/w.

Disodium Tetraborate is present in very low levels (<1%) in the anodic cleaner on our cadmium plating line and thus is very unlikely to be deposited on the finished plated components at levels exceeding 0.1% w/w.

In the case of lead indium plating the lead plating solution employs lead fluoroborate (23%) although this is not what is deposited on the finished coated part, and thus the resultant amount of the finished article should be less than 0.1% w/w.

Finally, Turco 4215 (used as an aqueous cleaner on most of our process lines) apparently includes sodium tetraborate pentahydrate, which is on the SVHC list.  Again, though, as this is used in initial stages of processing as a cleaner, and subsequently rinsed off prior to further chemical processing, it is unlikely to be present on finished components at all and almost certainly at levels below 0.1%.

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