Measuring pH on metallic planar surface

[Patrick Rota]

We are currently trying to measure pH levels on the (wet) surface of metals as part of a study about corrosion.
The surface may have a non-conductive protective layer.

- is it feasible to measure pH on a planar surface (dry or wet)? Which kind of sensor probe can be used for this task?
- which order of magnitude will be the measure? (precision of the sensor)

Any advice would be greatly appreciated!

 

[DrDu]

My first thought would be to use and indicator in combination with a spectrophotometer.

 

[Patrick Rota]

Thank you DrDu, this is a great idea, indeed.
Can you recommend some indicator? Do you have suggestions?
EDIT: we need an indicator for prolonged use (years), if it exists

 

[DrDu]

The choice of the indicator will depend on the pH range you are interested in.

 

[Patrick Rota]

Dear DrDu, thank you for your insight. Let me find out what is the pH forecast range.