Business Guide to Safer Chemicals 2018: Hard choices

Hexavalent chrome (Cr(VI)) is widely used in industry. Almost all chromium ore is processed via hexavalent chromium, mainly the sodium dichromate salt, though other compounds, including chromium trioxide and various chromate and dichromate salts are also known. Key applications for Cr(VI) include:

  • chromate pigments in dyes, paints, inks, and plastics;
  • chromate anticorrosive agents in paints, primers and other surface coatings; and
  • chromic acid electroplated onto metal parts to provide a decorative or protective coating.

Hexavalent chrome is also formed in certain industrial processes, such as when welding on stainless steel or melting chromium metal. Workers who handle chromate-containing products or who grind and weld stainless steel are particularly exposed to it. As a heavy metal that cannot decompose in nature, Cr(VI) can accumulate in dangerous quantities via the food chain if it ends up in drinking water or wastewater. It was in this respect that it is best known globally, because it was at the centre of one of the most notorious environmental scandals involving chemicals ever to happen in the US. In 1996, the Pacific Gas & Chemical Company settled a case for $333m, after many years in which Cr(VI)-containing wastewater from a cooling tower in the compressor station at Hinkley, California, was discharged over many years to unlined ponds and seeped into groundwater, affecting a wide area. Cr(VI) is highly toxic substance and is the most toxic form of chromium, because cells in the human body can mistake it for much-needed sulfates. Those who are exposed to it are at increased risk of developing lung cancer, asthma and skin damage.

REACH drives substitution

Chromium trioxide is a SVHC under REACH for its carcinogenic and mutagenic properties and is subject to authorisation. The use of Cr(VI) in electronic equipment is already banned in the EU via the RoHS Directive. The need for authorisation under REACH and consequent costs is prodding companies to look for alternatives. The European Chemicals Agency (ECHA) is also offering some incentives and support. One such company is Savroc of Kuopio, Finland, a technology provider that is active in hard chrome plating. Savroc has just spent two years proving its technology on an industrial scale, working with its largest customer, Tecnocrom Industrial, a plating company in Barcelona. The company’s goal is to license and implement its patent-pending technology. It raised €1 million in additional funding from investors in August 2017 in order to build a new technology centre and expand international sales. The centre has since been completed. Partly funded by Finland’s Centre of Economic Development, Transport and Environment, this has two plating lines and can provide customers with training and testing services, and samples. This year, says chief technology officer Juha Miettinen, the company is negotiating license sales and “we have a few new industrial installations going on”.

Trivalent chrome plating

Savroc’s technology replaces the hexavalent chromium used in hard chrome plating with trivalent chromium (Cr(III)). The different chemical properties of Cr(III) mean that is much less toxic. So, because its process uses REACH-approved chemicals throughout, the company believes its solution can help plating companies to compete, despite REACH restrictions. “The use of a trivalent chrome electrolyte ensures there are no REACH compliance problems with the chemistry, because the process is completely hex chrome-free,” says Mr Miettinen. “And because our plating process uses a standard electrolytic method, the same methods can be applied.” It also means that customers can use a familiar process, changing only the chemistry. There are Cr(III)-based coatings on the market, says Miettinen, but these are mainly used for decorative purposes and have found limited applications because of their poor mechanical properties. Savroc’s solution is to use a proprietary TripleHard additive that facilitates plating of 1,700 Hv hardness. This is not just sufficient for industrial applications, it is also significantly above of the 1,000 Hv of standard Cr(VI)-based plating. As well as standard electrolytic processes, the technique also uses a thermal pulsation treatment. According to Mr Miettinen, this produces internal diffusions and phase transformations inside the chrome layer. This “kind of multi-phase structure” in the coating stack “transforms the hardness of these layers stacks. This decreases as a function of depth, resulting in a sort of elasticity function,” he says. While the chrome coating can be added directly to a steel base, the company particularly promotes the additional use of nickel under-layers, which significantly increase the anti-corrosion properties of the coating. Thus, says Mr Miettinen, the process not only avoids authorisation fees for REACH compliance but provides financial benefits longer-term because “better mechanical properties result in less maintenance”.

Future plans

The company has five patents pending, for which it is making applications in eight regions worldwide. “So far we have not found any one-to-one competitors in the market,” says Mr Miettinen, which “gives us a remarkable competitive edge. Legislation is also a really strong driving force for us. These regulations force customers to switch to greener, safer chemistry and toxic-free alternatives,” he adds. The process has to date produced automotive parts, cylinders, hydraulics valves, pistons, shock absorbers and even shotgun barrels and grenade mortars. “The current focus is with hydraulic cylinders because of the anti-corrosion properties we can produce and because this is a high-scale business,” Mr Miettinen says. “However, we have also passed a customer’s shooting tests on gun-barrel applications.”

How are companies in the chemicals industry addressing the complex and practical challenges of making safer chemicals?

Chemical Watch, 12 November 2018 ; http://chemicalwatch.com