White spotting on silver coins - Matthew Williams, The Royal Mint
Add to calCardiff University School of Engineering
Matthew Williams
Director of Engineering and Quality, The Royal Mint
White spotting on silver coins
Tuesday the 25th of November 2025 at 18:00
Room N1.32 School of Engineering, Cardiff University, 5 The Parade, Cardiff, CF24 3AA
**Note this is not our usual room! N1.32 is on the first floor of the North Building, opposite the Trevithick Building. Please note that it is necessary to pay for parking, instructions are displayed on signs in the car park.
The lecture will also be streamed live, to register please use this link:
events.teams.microsoft.com/event/926d51c1-f30f-4235-9ebd-adba591ec9c6@bdb74b30-9568-4856-bdbf-06759778fcbc
Abstract
The occurrence of white spotting on silver coins remains a significant quality concern for the minting industry. These surface defects, often associated with sodium chloride and other atmospheric contaminants, compromise both the visual appeal and long-term stability of silver products. In this work, we have developed and implemented an invisible barrier coating to mitigate the interaction between silver surfaces and environmental species responsible for white spot formation. The coating provides a protective, non-intrusive layer that preserves the natural appearance of silver while preventing chloride adsorption and subsequent corrosion pathways. This advancement represents a step change in surface engineering for coinage, offering improved product reliability and customer satisfaction. By embedding this protective technology within the minting process, we aim to enhance product performance, reinforce brand reputation, and secure greater market competitiveness.
Biography
Dr. Matthew Williams is Director of Engineering & Quality at The Royal Mint, leading engineering, energy, quality, security, SHE, and operational excellence. He has over 15 years’ experience in the metals and manufacturing sectors, with expertise spanning operations management, metallurgy, and continuous improvement. Previously at TIMET, part of Precision Castparts Corporation, he led large operational teams of 100+ staff and championed the Zero Defects programme driving process innovation. Matthew began his career at Tata Steel and completed a PhD with Swansea University and Rolls-Royce, researching ultra-high strength steels. He is passionate about digitalisation, sustainability, and embedding quality excellence across high-value manufacturing.
