Hexavalent chromium is a toxic and carcinogenic chemical that is commonly used in the plating on plastics (PoP) process, during the surface etching step, as well as the electroplating step to achieve a decorative or protective finish on plastic parts. The substitution of this chemical, however, is crucial and will contribute to increasing the safety and sustainability of the process.
Considering the electroplating step, several alternatives to hexavalent chromium have been developed, such as trivalent chromium, which is less toxic and considered environmental friendlier. Trivalent chromium can be used in the PoP process during the electroplating step to achieve similar finishes, as far as the decorative and corrosion resistance properties are concerned. Trivalent chromium also has better adhesion to plastic substrates compared to hexavalent chromium, which can improve the durability and performance of PoP coatings.
Non-chromium finishes, such as nickel, copper, zinc coatings are also alternatives to hexavalent chromium. These coatings can provide similar corrosion resistance and durability properties, while offer better environmental and health profiles. The FreeMe project has adopted this approach as far as the electroplating step is concerned, using mainly nickel coatings. In addition, FreeMe proposes an alternative to the use of hexavalent chromium in the surface etching step, by using REACH compliant chemicals.
What is more, there are also alternative processes to electroplating, such as physical vapor deposition (PVD) and chemical vapor deposition (CVD), which do not require the use of toxic chemicals or heavy metals. These processes can be used to deposit a wide range of metals and alloys onto plastic surfaces, which can provide high-quality and durable coatings for various applications. Even though these processes can achieve the deposition of metallic coatings without the use of hexavalent chromium in neither an etching step nor in electroplating, they require a completely different equipment and a large investment. This means that the cost for the coating deposition would be significantly increased and many plating shops would not be able to follow this transition. It is important for plating shops to comply with regulations and meet sustainability goals, adopting solutions that could be easily fitted into the existing plating process, and would require a reasonable investment.
Overall, the use of alternative coatings and processes to substitute hexavalent chromium in POP is becoming more common as companies seek to improve their environmental and health profiles and comply with regulations. However, many aspects shall be considered regarding the feasibility of the proposed solutions and their adoption by the plating industry.