While most brush plating solutions produce high quality deposits when plated in the plating temperature range of 60 °F to 120 °F, a few solutions must be plated within a tighter temperature range or at higher temperatures to provide the desired thickness, quality, and deposit characteristics (e.g., alloy composition).
In addition to having the solution (bath) within the proper plating temperature range throughout the operation, getting to and maintaining the correct temperature in the work area is also important. The work area is the thin film of solution on the work piece where plating is taking place. There are four factors that influence the temperature in the work area:
- Temperature of the part.
- Temperature of the solution being used.
- Heat developed in the work area during plating.
- Amount and exchange of solution being supplied to the work area.
Temperature of the part is a concern when plating large parts which can quickly chill a preheated solution. In these cases, temperature is largely controlled by heating the part to the proper temperature prior to plating.
Alternately, temperature of the solution becomes a concern when plating thin or smaller parts that can be rapidly heated by a warmed solution.
When using solutions plated at higher voltages (over approximately 12 volts), plating at high currents, or plating higher thicknesses of deposit, the heating effect from the passing current is a factor. The amount of heat developed, while plating, is proportional to the voltage used, multiplied by the current passed:
Heat = Volts x Amps
The developed heat is typically sufficient to quickly heat the work area, tool and solution. But, in some cases, heat from plating can result in excessive temperatures in the work area, causing the tool to overheat. This is characterized by:
- The plating tool, part and solution becoming noticeably hot.
- The current diminishing as plating continues.
- Raised voltage leading to decreased amperages.
- Using a larger pump.
- Increasing the size or number of solution distribution holes in the anode.
- Decreasing the thickness of the cover.
- Starting with more solution.
How fast and how much solution is supplied to the work area is the last factor. Rapid supply of solution to the work area tends to keep the work area closer to the temperature of the solution being used. Less rapid supply allows the work area to be heated more rapidly. An example of how rate of solution supply can be manipulated is the case where the heat generated from plating is relied on to heat the work area. This technique is used with solutions that plate better at high temperatures, but which are not preheated. When starting out, low rates of solution supply are used. This helps keep the heat developed in the work area. This permits the voltage and amperage to be raised sooner without a burned deposit resulting. This in turn develops more heat. The net result is that the proper elevated temperature is reached sooner. The solution supply then is increased to prevent the work area from overheating.
Diligently monitoring the factors that influence the plating temperature of the work area will produce a quality, deposit without issue. If you have questions or concerns about maintaining the proper temperature of your work area, contact our Technical Service Department at 800-465-4131 or email@example.com.