Chrome plating refers to the process of electroplating a thin layer of chromium onto a metal surface to provide protection and a shiny, mirror-like finish. While this versatile plating technique has been used for decades on everything from car trim to plumbing fixtures, chrome plating has come under scrutiny due to its potential health and environmental impacts.

Chrome Plating

Chrome plating involves submerging the metal component in a chromic acid solution and applying an electric current to induce the chromium particles to bond to the surface. The thickness of the coating can range from 0.5 microns up to several millimeters.

There are two main types of chrome plating:

Decorative chrome plating – Thin layers, usually 2-3 microns, are applied to provide a bright, shiny appearance on surfaces like automotive parts, furniture fixtures, and household appliances.
Hard chrome plating – Thicker layers up to several hundred microns are plated on industrial components like hydraulic cylinders, rollers, and engine parts to improve wear and corrosion resistance.

The lustrous finish and protective qualities make chrome attractive for decorative and functional applications across many industries. However, the process of chrome plating comes with some significant downsides when it comes to health and environmental risks.

The Use of Hexavalent Chromium

At the crux of the controversy around chrome plating is the use of hexavalent chromium, also known as chromium VI or Cr(VI). This carcinogenic compound is used as a key ingredient in the chromic acid plating solutions.

During the plating process and when cleaning and maintaining the plating tanks, hexavalent chromium is emitted into the air and discharged in wastewater streams. Acute exposure can cause eye, nose, and throat irritation, while long-term exposure has been linked to lung cancer, kidney damage, and reproductive issues among workers.

The toxic impacts of hexavalent chromium extend beyond just the plating facilities. Air emissions can spread into surrounding communities. Improper disposal of plating waste has resulted in chromium contamination of drinking water supplies like in the case of the Erin Brockovich story.

These severe health risks have been the main driver of efforts to regulate or eliminate the use of hexavalent chromium in chrome plating operations.

Regulations Restricting Hexavalent Chromium Use

Given the health hazards posed by hexavalent chromium exposure, governmental agencies have enacted regulations that restrict or prohibit its use in certain contexts.

California’s Ban on Hexavalent Chromium Plating

One of the most comprehensive bans has been instituted in the state of California. In 2011, the California Air Resources Board (CARB) introduced a strict regulation that phases out the use of hexavalent chromium in decorative and hard chrome plating applications by 2024 and 2040 respectively.

This statewide ban was enacted after data showed that chrome plating facilities accounted for more than 90% of hexavalent chromium emissions in California. Monitoring studies found chromium levels near plating plants that exceeded public health standards by hundreds to thousands of times.

The phase-out period gives businesses time to adopt alternative plating technologies while still achieving the urgent goal of reducing toxic emissions. CARB estimates that meeting the hexavalent chromium ban will save over $20 million in health costs.

EU Directives on Hexavalent Chromium Authorization

The European Union has taken regulatory steps to curb the risks of hexavalent chromium as well. Directive 2004/37/EC established binding occupational exposure limits for chromium VI compounds.

This was followed up by the REACH Authorization in 2017 which requires companies to obtain explicit EU authorization before using hexavalent chromium in manufacturing processes like chrome plating. Authorization is only granted if the company can demonstrate that no suitable alternatives exist and that the risks are adequately controlled.

The intention behind this regulation is to promote the transition to safer substitutes for hexavalent chromium across all industries. Companies applying for authorization need to have specific plans in place for eventually phasing out its use.

OSHA Standards for Workplace Exposure

In the United States, while there is no federal ban on the use of hexavalent chromium in plating, the Occupational Safety and Health Administration (OSHA) has strict Permissible Exposure Limits (PEL) to protect workers from exposure risks.

The PEL for airborne hexavalent chromium is 5 micrograms per cubic meter of air averaged over an 8-hour shift. Facilities that use chromium also need to implement engineering controls, workplace hygiene practices, and regular employee health monitoring to comply with OSHA regulations. Failure to comply can result in hefty penalties.

Alternatives to Hexavalent Chromium Plating

Given the regulatory landscape, the chrome plating industry has been investing in alternative processes that do not rely on hexavalent chromium. However, replacements have been slow to gain traction because it is challenging to match the performance qualities of chrome plating.

Here are a few of the most viable alternatives:

Trivalent chromium – Uses chromium in the less toxic trivalent (Cr(III)) state rather than the hexavalent form. However, trivalent chromium baths have greater difficulty achieving thicker plating layers.
Nickel-chrome plating – Alternates layers of nickel and chromium rather than using solely chromium. Durability is not as high as hard chrome.
HVOF thermal spraying – Involves spraying fine chromium powder onto a surface using a hot combustion flame rather than electroplating. Mainly used on large industrial components.
PVD techniques – Physical vapor deposition (PVD) methods like sputtering or ion plating allow environmentally cleaner vacuum deposition of chromium instead of wet electroplating. Limited to smaller parts with thin coatings.
Anodizing – Creates a protective aluminum oxide layer on the surface of aluminum components. Does not provide the same decorative finish as chrome.

While these alternatives help address health and environmental issues, most do not offer the same versatility and high-performance capabilities as conventional chrome plating. More innovation is needed to develop a perfect replacement.

Outlook for the Future of Chrome Plating

Chrome plating has faced rising scrutiny due to its impacts on human health and the environment. However, this versatile metal finishing technique still remains in widespread use globally due to its unparalleled aesthetics and engineering properties.

Rather than an outright ban, the approach taken by most regulatory agencies has been to mandate stricter control measures and phase out the most hazardous chemical – hexavalent chromium. There is optimism that new technologies can emerge to allow chrome plating to continue serving critical functions in modern industry while mitigating its risks.

However, eliminating hexavalent chromium entirely remains a challenge. Some applications may still warrant its use and exemptions are granted if proper authorization procedures are followed. Facilities must demonstrate that worker exposures are minimized and waste is properly contained.

Finding alternatives that meet the performance demands of high-tech industries represents the biggest hurdle. But with increased investment and research, there is hope that safer, more sustainable forms of chrome plating can be developed. Strict regulations have accelerated the impetus to phase out hexavalent chromium, but collaboration between government, industry and scientists will be key to making this transition possible while still harnessing chrome’s capabilities.

References

[1] California Air Resources Board. “Hexavalent Chromium Plating Regulation.” https://ww2.arb.ca.gov/our-work/programs/hexavalent-chromium-plating/hexavalent-chromium-plating-regulation

[2] European Commission. “Hexavalent Chromium Restrictions.” https://echa.europa.eu/applications-for-authorisation-previous-consultations/-/substance-rev/2490/term