What is pH and Why is it Important?

pH is a number that determines the acidity or alkalinity of an aqueous solution. The numeric value represents the concentration of hydrogen ions (H+) present in the solution. When the temperature is 77°F, a solution with a pH greater than 7 is considered “alkaline” (such as baking soda), a pH of 7 is “neutral” (such as water), and a pH under 7 is considered “acidic“. These values can shift depending upon the temperature of the solution. While the pH range is typically given as zero to 14, pH can be less than 0 or greater than 14. These numbers represent a ten-fold change in the number of hydrogen ions. A pH of 3 is ten times more acidic than a pH of 4.

The pH of a solution is crucial in electroplating for several reasons:

1. Uniformity. The right pH level for a solution ensures that the finish will be smooth and consistent all over the part.
2. Electrochemical Reactions. The right pH level for a solution ensures the optimum impact of electricity within a tank.
3. Controls Impurities. The right pH prevents impurities from interfering with the plating process.
4. Adhesion. The right pH assures that the finish will properly adhere to the part.
5. Maintenance. Maintaining the right pH extends the life of a bath.

Each bath in a plating shop is regularly tested for pH. If the pH for a bath is too low, making it acidic, the pH is increased by adding a chemical like sodium bicarbonate. If the pH in a bath is too high, making it alkaline, the pH can be decreased by adding a chemical like sodium bisulfate. Water circulation and filtration are also important for the maintaining of proper pH.