Blood pressure is usually expressed in terms of the systolic pressure (maximum during one heart beat) pressure over diastolic pressure (minimum in between two heart beats) and is measured in millimeters of mercury (mmHg), above the surrounding atmospheric pressure (considered to be zero for convenience).
Corrosion on the terminals is due to hydrogen gas being released from the acid in the battery. It mixes with other things in the atmosphere under the hood and produces the corrosion you see on the terminals. Generally, if the corrosion is occurring on the negative terminal, your system is probably undercharging.
Sulfation occurs on the negative post in this condition. If corrosion was on the positive post, that would indicate a consistent over-charge condition. But an under-charge is sort of expected in a car, as the battery is charged and discharged quite a bit. As such, rarely is it at full charge.