Making Chrome Safe

SAFE Chrome is a different approach than that taken by traditional trivalent solutions. It uses an ionic liquid-based chemistry to reduce Cr3 to Cr0 in an easier way.
Photo Credit: Trion Coatings LLC

Trion Coatings LLC of South Bend, Indiana, is on a mission to provide the finishing industry with safe and environmentally sustainable functional and decorative chrome coatings that match the performance of hexavalent chromium-based solutions. The company believes it has the answer in a new, non-aqueous, trivalent chromium chemistry called SAFE Chrome.

Not to mix metaphors, but the quest to replace hexavalent chromium (also known as hex chrome or Cr⁶) has been both a sore subject and a bit of a holy grail for the finishing industry for decades. Widely used in coating systems for both decorative and functional applications, hex chrome offers excellent hardness, wear resistance, corrosion resistance and enhanced adhesion to substrates. However, hex chrome is proven to be carcinogenic and poses occupational and environmental hazards that has cost the industry hundreds of millions of dollars over decades. Compliance with increasingly stringent regulations has been a continuous struggle for plating operations and the future viable use of hex chromecontinues to be a major concern for the metal finishing community.

SAFE Chrome meets standards for commercial specifications and functional applications while providing a safe operating environment for employees.
Photo Credit: Trion Coatings LLC

Many platers recall the year 2006, when OSHA lowered the Permissible Exposure Limit (PEL) for hexavalent chromium from 52 micrograms per cubic meter (µg/m³) to 5 micrograms per cubic meter (µg/m³). This widespread regulatory action occurred on the heels of previous ACGIH and NIOSH studies and recommendations.

Below are recent changes in recommended worker exposure limits to Hexavalent chromium:

2013 – The National Institute for Occupational Safety and Health (NIOSH) published a new Recommended Exposure Limit (REL) of 0.2 micrograms per cubic meter for hexavalent chromium to workers.

2018 - The American Conference of Governmental Industrial Hygienists (ACGIH) published a new Threshold Limit Value (TLV) of 0.2 micrograms per cubic meter for hexavalent chromium exposure to workers.

2022 and beyond – Will OSHA publish a change from its current PEL of 5 micrograms per cubic meter? History may suggest it is likely. A change to 0.2 micrograms per cubic meter would result in a 25 fold reduction from the current rule.

Trion set out to develop a trivalent chromium solution that checked all the boxes — safety, performance, cost. The company collaborated with several recognized industry partners including Nucor Steel, Imagineering Finishing Technologies, Surface Technology Inc., and KCH Surface Finishing.

“We’ve got a group of people who bring different skill sets to the table, and have been helping us guide the technology in its development now for more than 18 months,” says Doug Morrison, president and co-founder of Trion Coatings. “They were interested in doing the next type of chrome plating — something that perhaps gets the regulatory issues addressed.”

Trion says its SAFE Chrome trivalent chromium solution meets standards for commercial specifications and functional applications while also providing a safe operating environment for employees. It is RoHS (Restriction of Hazardous Substances) compliant, contains no Cr⁶ and is made without PFOA or PFOS, which is also emitted in the hex chrome process, and is its own source of regulatory scrutiny that has garnered significant attention from the EPA as it relates to its presence in myriad industries.

Hex chrome phase-outs on the horizon?

This past year, metal finishers in California have been in talks with the California Air Resources Board (CARB) over a proposed phase-out of hexavalent chrome use in the state for both decorative and functional finishing applications. At the time of this writing, aggressive initial deadlines have been pushed out as the negotiations continue. Metal finishers in the state say the measures could force finishing operations to relocate or even close their doors, potentially causing functional coatings used for critical applications to become more expensive or even unavailable. Regardless of the outcome of the proposed California legislation, the future of hexavalent chrome is likely to be a topic of contention in the industry for some time. This has led many finishers to at least investigate trivalent chromium alternatives, both for decorative and functional applications. Several water-based trivalent solutions have come to market, but there have been many hurdles to replacing hex chrome from cost to meeting performance specifications, and to this day there has not been a viable replacement from a performance standpoint that can replace functional uses of hex chrome.

A bit of chemistry

SAFE Chrome is a different approach than that taken by traditional trivalent solutions. Morrison explains that traditional trivalent solutions are water-based chemistries that require additives that aid in reducing trivalent chrome to chrome metal. SAFE Chrome uses an ionic liquid-based chemistry to reduce Cr³ to Cr⁰ in an easier way.

With aqueous-based trivalent chemistries, the Cr³ion is trapped inside of a highly stable bi-pyramidal complex. Because of this, the process of reducing the Cr³in these systems causes hydrogen evolution at the cathode, which rapidly changes the pH of the solution. “You have all of these side reactions with all of these other components of that aqueous chemistry. So it's not just water in the Cr³, it's water, Cr³and five other ingredients to disrupt that bi-pyramidal complex.”

SAFE Chrome’s ionic liquid chemistry simplifies things. Morrison explains, “We’ve got basically three ingredients water, ionic liquid and chrome. We only have to manage these three ingredients and the ionic liquids disrupt that water Cr³ion complex. Because of that, we’re able to produce Cr³at lower voltages, and we’ve got less hydrogen evolution and less pH evolution.”

Total cost of ownership

One of the biggest concerns many finishing operations have regarding a switch to trivalent chromium is cost. Traditionally, switching from hexavalent to trivalent chromium was an expensive proposition for shops, and the sticker shock at the initial investment in new equipment and chemistry has been a deterrent for many finishers in the past. Trivalent chemistries have been evolving and chemical suppliers have been making strides toward making the total costs lower.

Trion Coatings set out to make switching to SAFE Chrome as easy a transition as possible. The solution is designed to use similar equipment often used in existing hexavalent chromium lines.

“From the beginning, we were committed to developing a technology that would be a drop-in replacement to the extent it could be,” says Morrison. “As a result, we now have a process that uses standard direct current rectification; uses no exotic materials; works without the use of hazardous lead anodes, works in open-air settings; and is an industrial compatible and robust technology. That’s been the mission from day one.”

He adds, “You may have to replace the liner of a tank, you may need to adjust the rectification size. But you’re still using direct current rectification. We’re not using pulse plating or things of that nature. Depending on the application and State requirements, there’s likely no need to change an existing exhaust system or racking.”

In addition to trying to keep the up-front investment in new equipment and chemistry as low cost as possible, Morrison says that the lifecycle costs of a plating line need to be taken into consideration when evaluating an investment in SAFE Chrome. This includes the cost of electricity, not just the capital equipment and the operational expenditure. SAFE Chrome’s increased plating rate allows it to provide build thickness more quickly and with a much lower cost of electricity to plate. In other words, the initial capital cost of the transition in terms of the investment in the chemistry and some adjustments in the equipment is quickly offset by a lower cost of operation.

“When you factor that in, your cost goes down significantly,” Morrison says. “Your total cost of ownership is lower, the plating rate is faster, and the efficiency is better.”

Another cost consideration to factor in is insurance coverage. As regulations continue to ramp up, an increasing number of finishing operations may find themselves having trouble finding liability insurance and workers’ compensation insurance that will cover operations that use hexavalent chromium.

“If you’re able to get hexavalent chromium out of your shop and not expose your workers to the risks associated with it, you’re going to be able to keep your premiums where they are — maybe reduce them,” Morrison says.

Performance

At the end of the day, the real question comes down to performance. A cost competitive solution offering environmental sustainability won’t replace a time-tested process if the coating itself doesn’t achieve the desired results.

Trion Coatings says SAFE Chrome can meet the specifications required of thin dense chrome (TDC). In terms of wear resistance, SAFE Chrome exceeds the AMS 2438 requirement. Taber Abrasion testing of the coating yielded sub 1.0 mass loss and the coating outperforms hexavalent chromium in Falex Pin and VeeBlock testing.

Further, the coating is ready for a wide range of functional applications from automotive to medical to construction and agriculture to aerospace and defense. In fact, Trion Coatings recently announced a Cooperative Research and Development Agreement (CRADA) with the U.S. Army Combat Capabilities Development Command Armaments Center (DEVCOM) to explore utilizing SAFE Chrome for defense applications.

Of course, when it comes to completely replacing hexavalent chromium there remains plenty of work ahead. Qualification of new materials for high performance applications such as aerospace is rigorous. Looking to transition trivalent chrome to an application such as aerospace landing gear is going to take time.

Finishers are working to educate regulatory committees such as CARB that set timetables for mandating a switch from hexavalent chrome to trivalent should be based on the specifications required of each application. That’s an important point for the evolution of trivalent chemistries. Perhaps rather than chasing our tails over a non-existent one-size-fits-all solution, thinking of trivalent chromium in terms of matching the right material to the right application is the best way to move forward.

Morrison says, “We have worked hard to develop and enhance our technology and we are now excited to be positioned to support the metal finishing industry transition away from hex chrome in a supportive way that will position those businesses for long-term safety and success.”

Want to learn more about Trion’s SAFE Chrome trivalent solution? Dig deeper in an episode of Products Finishing’s On the Line podcast. Visit short.pfonline.com/OTL15.