![]() These issues can primarily be avoided through proper setup of the system, regular preventative maintenance and testing, and a solid working relationship between the client and chemistry supplier.In this communication, we present a generalization of our investigations concerning current state in the development of trivalent chromium baths as an environmentally friendly alternative to hazardous electroplating baths containing extremely toxic hexavalent chromium compounds. To recap, when experiencing dark streaks or deposits out of trivalent chromium plating solutions, common causes to look for are high metallic impurities, complexer imbalance, insufficient or older technology anti-mist additive, and improper balance in proprietary salts. Modern formulations of proprietary salts experience much less drifting and require much less adjustment by the customer, making the process more user friendly. This is often dependent upon the technology behind the proprietary blend offered by the chemistry supplier. While the proprietary salts are consumed through dragout, the proprietary additives may start to drift over time. Every six months, it is necessary that the chemistry supplier perform a complete analytical breakdown of the proprietary salts and provide the customer with proper adjustments, if necessary. It’s important to make sure the proprietary salts are operating at or near 100% of the recommended parameters at all times, in order to ensure the components are at an optimum. The proprietary salt blend also contains additives that improve high-current density buffering and specialty additives that prevent the chromium from converting from trivalent to hexavalent. These proprietary salts are designed to provide the necessary conductivity of the solution. This is often the more challenging factor because it relies upon a trusted relationship between the customer and a knowledgeable chemistry supplier. ![]() Improper Proprietary Salt Balance: A final cause behind dark streaks or deposits is the blend of proprietary salts. When the anti-mist additive is not sufficiently maintained or relies on older technology, the deposit distribution can be affected, leading to a darker deposit or dark streaks. ![]() Please refer to your supplier’s recommendations for specific anti-mist ranges as these components can vary from supplier to supplier. The anti-mist additives are generally consumed in very small amounts and can be analyzed using a tensiometer or any other means to check surface tension in the solution. The graphs in Figure 1 show the comparison of deposit distribution through the use of older technology anti-mist versus modern technology anti-mist additive. Modern (newer technology) anti-mist additives also provide additional resistance to metallic contamination. ![]() Insufficient Anti-Mist Additive: Anti-mist additives are designed to lower the surface tension of the working solution and improve deposit distribution. This can be achieved by heating the solution to 140☏ for 4-8 hours and then cooling it to the recommended operating temperature. It is important to ensure the solution contains the correct amount of complexer and, finally, that the chromium in solution is fully complexed. Additionally, some suppliers have modern technology mist suppressants that not only lower surface tension but also provide high tolerance to metallic impurities.Ĭomplexer Imbalance: Chrome that is not fully complexed will not bind and will cause dark patterns, so it is necessary for trivalent chromium solutions to contain a complexer that enables the chromium to plate correctly. It is also necessary to regenerate the ion exchange resin regularly to ensure optimum effectiveness to continually pull metals out of the solution. To remove metallic contamination, it is critical to ensure the ion exchange is properly sized to the trivalent chromium solution and, most importantly, to utilize a high quality resin that has a strong affinity toward metals, such as copper, nickel and zinc. Lastly, iron contamination can be looked into as a factor in causing dark deposits. Copper and zinc contamination mainly come from brass substrates and zinc die cast where unplated surface area dissolved in the trivalent chromium plating solution due to low pH. Nickel contamination is the most common as the nickel solution can drag down the plating line and find its way into the trivalent chromium solution. The most common types of metallic contamination are nickel, copper, zinc and iron. Metallic Contamination: Unlike hexavalent chromium solutions, trivalent chromium plating solutions are especially susceptible to metallic contamination. Reduced Ion Electroless Nickel to Meet a Sustainable Futureĭark patterns in trivalent chromium plating can be caused by the following:
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