Understanding Nickel Release in Gold-Plated Stainless Steel: Navigating Allergy Risks

Introduction

When it comes to gold-plated jewellery, understanding the risks associated with nickel release is critical for manufacturers and consumers alike. Nickel allergies are a common concern, and the composition and treatment of metals play a pivotal role in mitigating these risks. Today, we delve into the complexities of nickel release from gold-plated 316 stainless steel and explore how to ensure compliance with EU nickel regulations.

Corrosion and Sensitisation

316 stainless steel, known for its corrosion-resistant properties, typically aligns with EU nickel release regulations approximately 95% of the time. However, when it undergoes gold plating, the compliance rate may drop. The root cause of metal-induced skin sensitisation is corrosion, which leads to the formation of soluble ions such as nickel. In the absence of corrosion, the risk of skin allergy is negligible.

The key to stainless steel's corrosion resistance lies in its chromium content. To merit the 'stainless' label, the steel must contain more than 10.5 wt% chromium—ideally between 17-18 wt% for enhanced corrosion protection. Chromium interacts with oxygen, often in sweat, to create a passive, protective film over the steel, effectively limiting nickel release.

The Galvanic Reaction Challenge

The complication arises with gold-plated steel. Should the gold plating contain micropores, it becomes susceptible to galvanic reactions, particularly in the presence of sweat. This reaction accelerates the corrosion process, markedly increasing the potential for nickel ion release, sometimes up to tenfold, based on the porosity level of the gold layer.

The principle behind galvanic reactions is the interaction between two disparate metals—in this instance, the noble gold and the less noble components of steel—when an electrolyte such as sweat is present. This interaction favours the corrosion of the less noble metal, which in jewellery often translates to increased nickel release.

Addressing the Risks

To counteract this, a viable strategy is the application of thicker, impervious gold plating. This method enhances corrosion resistance and acts as a formidable shield over the steel, significantly reducing the chances of galvanic corrosion. Thicker plating thus not only elevates the aesthetic value but also reinforces the safety aspect by curbing nickel release.

Manufacturers need to consider these factors when designing gold-plated stainless-steel jewellery. Ensuring non-porous, thick gold plating can be the difference between a piece of jewellery that's simply beautiful and one that's both beautiful and safe to wear.

For consumers with nickel sensitivities, it's equally important to be informed about the materials, processes used and allergy safety testing performed on your jewellery. When in doubt, seeking pieces with thicker gold plating may provide additional assurance against potential allergies.

Conclusion and Recommendations

In conclusion, while un-plated 316 stainless steel generally poses no significant allergy risk, the introduction of gold plating requires careful consideration to maintain this safety standard. By addressing the potential for galvanic reactions through improved plating techniques, the industry can continue to offer lustrous, gold-plated options without compromising on consumer well-being.

Authors Profile

Dippal Manchanda, with a distinguished career spanning 38 years, is recognised as an authority in the precious metals and fashion jewellery industry. Manchanda, who holds a Master of Science degree in Chemistry, is accredited as a Chartered Chemist (CChem), Chartered Scientist (CSci), and a Fellow of the Royal Society of Chemistry (FRSC). His involvement with the International Organization for Standardization (ISO) is significant, especially in the Technical Committees for Jewellery, Precious Metals, and Horology. As the lead for the ISO 10713 gold plating standard project, Manchanda plays a critical role in shaping industry standards. He also actively contributes to European Committees concerned with metal allergens and jewellery standards. Within the UK, Manchanda chairs the British Standards Institution (BSI) Jewellery Committee and is an integral member of the CIBJO Precious Metal Commission Steering Committee. His extensive expertise also extends to collaborations with UK Trading Standards and Scotland Police, where he offers vital technical support and serves as an expert witness.