Management Considerations of Alkaline Tin Plating Bath
Introduction
The process of providing a metal substrate with a protective coating of tin with alkaline tin plating is becoming increasingly important as industrial processes progress and outdate the more traditional methods of plating. Until now, the conventional wisdom was that acid tin plating produces superior finishes, superior corrosion protection and superior adhesion properties to the substrate.
However, with alkaline bath processes, it is now possible to obtain similar high-quality characteristics, with even enhanced corrosion protection. This has led to an increased demand for alkaline tin plating, and as a result, manufacturers are now paying closer attention to the maintenance of their alkaline baths.
Maintenance
The most effective way to properly maintain an alkaline tin plating bath is to come up with a formalized bath maintenance schedule. This should include regular monitoring of the baths physical properties, such as temperature, alkalinity and pH. Additionally, the bath should be changed out or treated with a cleansing agent about every 800 to1000 hours of use. Generally speaking, bath maintenance should be done every two to three weeks depending on the frequency of use.
When it comes to bath additives, manufacturers should pay attention to the specific requirements of their specific alkaline bath. Most alkaline tin baths require an additive on a regular basis. Common additives include:
• Ammonia – Ammonia is an important additive for alkaline tin baths and can be used to increase the pH of the bath and reduce the rate of oxidation of the tin ions.
• Boric acid – This is often used as a corrosion inhibitor and helps to slow down the rate of oxidation of the tin ions.
• Sodium bicarbonate – This is used to buffer the pH of the bath and is also used to control the deposition rate of the tin ions onto the substrate.
• Sodium chloride – Sodium chloride is used to reduce the conductivity of the plating bath, which in turn reduces the rate of deposition of the tin ions onto the substrate.
• Lysine – Lysine is used to reduce the attack of microorganisms on the tin surface and prevents the formation of pits on the substrate.
Finally, it is important to ensure that the bath is kept clean and that the temperature is kept within the optimal operating range. This will help to ensure the baths stability and consistent deposition of the tin ions.
Conclusion
In summary, the management and maintenance of an alkaline tin plating bath requires a series of regular maintenance tasks and the use of specific bath additives. Proper and regular maintenance of the bath is essential for ensuring the stability of the bath chemistry, as well as for obtaining a consistent appearance of the plated surface. Thus, it is essential for manufacturers to be aware of the specific requirements of their specific alkaline tin baths and to adhere to formalized maintenance schedules.
