What is ph?
pH measures how acidic or alkaline a solution is on a 0–14 scale, where 7 is neutral. In parts cleaning it is the first compatibility check: above pH 10 a cleaner attacks aluminium and zinc; below pH 5 it attacks steel. Most industrial cleaning runs at either 7–9 or 11–13.
The scale is logarithmic — pH 12 is ten times more alkaline than pH 11 and a hundred times more than pH 10. Small numeric changes are large chemical changes, which is why 'slightly more alkaline' is rarely a small decision on a mixed-metal line.
Working pH drifts in service. Alkalinity is consumed as it saponifies oil, and carbon dioxide from the air slowly neutralises the bath. A bath that started at pH 12 and now reads 10.5 has lost most of its cleaning reserve even though it still looks and smells the same.
Checking pH weekly with a meter or strips, alongside a titration for total alkalinity, is the cheapest bath-control routine there is — and it catches a failing bath before it produces a rejected batch.
