Definition - What does Buffer Capacity mean?
Buffer capacity is the amount of acid that buffers are capable of absorbing prior to breaking the capacity for adding strong acid. Solutions with a weaker base have more buffer capacity when adding a strong acid. Solutions with higher amounts of weak acid have higher levels of buffer capacity when adding a strong base.
Increased buffer capacity within a constant level of alkalinity within a pH range of 6.0 to 9.0 can reduce the rate of corrosion in steels, especially the mild form. However, increased buffer capacity in different levels of pH due to elevated alkalinity doesn't lead to reduced rates of corrosion as brought about by higher conductivity and ionic strength.
Corrosionpedia explains Buffer Capacity
The main purpose of buffers is to maintain the pH of solutions in a narrow range. In the buffer system, the higher the levels of HA and A- molecules available, the less effect in the pH system when adding a strong base or acid.
Even though the pH buffer is identified by the ratio of HA and A-, the capacity of a buffer to absorb a strong base or acid is identified by individual concentrations.