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.
:) In the case of a battery it is the two dissimilar metals (lead,copper and even the steel bolts) are caused to corrode... either by their mere presence, or by some 3rd party chemical.In this case, it is battery acid and the act of charging a battery. That is why most corrosion is found on the Negative battery post. The constant overcharging of the battery increase the corrosion.