EU REACH continues to identify and act on substances of very high concern (SVHCs), with previous blogs discussing specific cases around chromium trioxide, diarsenic pentoxide and the impacted products and applications containing these substances.
Boric acid and borate salts are SVHCs, and in July 2015 were recommended for inclusion in the Authorisation List (Annex XIV). According to the authorities, these substances could damage fertility and unborn children. This notification brought focus to the need to find effective alternatives in the vast range of products and applications that use boric acid and borate salts.
Currently, these salts are not being prioritised to be moved on to Annex XIV as specifically stated in the most recent update regulation (EU/2017/999). However, it is only a matter of time before these will move to Annex XIV.
Table 1: Boric acid and borate salts have been recommended for inclusion in the REACH Authorisation List (Annex XIV).
The nature of the toxicity intrigues many, given the historical widespread use of these substances. The descriptions of some products used, for example, as household cleaners, could be quite contradictory, with some being described as “green” and “ideal for household cleaning,” while identifying the potentially toxic nature of the substance.
Boric acid is widely used in electroplating manufacuturing for electrolytes that operate below 100% cathode efficiency, as an effective buffer, extending the range and stabilising the operation of the electrolyte.
As the current density approaches the limiting current, the presence of an effective buffer is critical to quickly eliminate the local build-up of hydrogen. Low (or no) boric acid will be obvious, with the deposit showing dark, pitted and nodular deposits. Solution flow at the electrode surface is also important as the current density increases, to ensure that all components and reaction products are moved to and from the surface efficiently.
This buffering system is used to stabilise the operating pH in many electrolytes, including zinc, nickel and chromium, which are widely used in decorative and functional plating applications.
Nickel electroplating is truly a global industry, with applications for wear and corrosion resistance stretching across electronic and industrial applications, from heavy engineering to the smallest of electronic components. The electrolytes from which parts are plated are fine-tuned to the specific needs of the plated part substrates, size, upstream/downstream applications, etc., and can be chloride, sulphate or sulphamate based, but almost all have the use of boric acid in common.
Boric acid electrolytes are very well known, with proprietary products having been used for generations of devices, all now facing the prospect of change. However, not only does one need to consider the buffering role when seeking an effective substitute, but boric acid, as used in nickel electroplating, plays a complex role, and one that is perhaps not fully characterised. Not only is pH buffering enabled, but the substance acts as a grain refiner impacting brightness, hardness, stress, adhesion, etc., depending on local parameters.
REACH Authorisation will impact the use of boric acid, but in today’s world, there are now overlapping regulatory-driven activities to create the more sustainable world we all desire. In the case of nickel, we have boric acid substitution activity, due to the pending REACH Authorisation, as well as, for some applications, the control or elimination of the use of nickel itself. Nickel use is already heavily regulated for applications or products involving contact with human skin, water and steam.
Other Plating Applications
In other applications, such as decorative chromium plating (e.g., car interior and exterior chromium-plated parts), most nickel and chromium electrolytes contain boric acid. Even trivalent chromium electrolytes, as replacement for the toxic hexavalent chromium, contain boric acid and will require an alternative buffer ahead of an Authorisation deadline.
For users of these plating products who may be operating a complex plating process, involving multiple metal layers for multiple end markets, the process of managing the replacement of boric acid will mean very significant activity and coordination to avoid (if possible) duplicate and costly replacement testing and qualification, layer by layer, application by application.
The list of SVHCs is long, and it is difficult to predict the order in which they are processed through the REACH system. There is scope for delay or change of priority as those involved in the substance use engage in the political process. As we’ve seen, extension of use beyond the sunset dates has been routinely permitted, through an effective submission for authorisation. These delays provide the time to create the new replacement/sustainable products, but perhaps delay the incentive for users to develop or test or adopt replacement materials.
Dow is fully engaged in the development of boric acid replacement electrolytes for nickel, and has shown that boric acid-free nickel plating can be achieved. The characteristics and performance of this exciting new nickel product are the subject of a future blog. Given the future SVHC regulation and related workload, we encourage those impacted by REACH to engage with Dow early to understand needs, sample new products and become compliant in a manageable time frame.