Water sample analysis and data interpretation are critical to internal corrosion prediction, especially with respect to CO₂/H₂S and organic acids corrosion. Misunderstanding of the water data is a frequent source of error in corrosion prediction. This paper provides guidelines on using water chemistry data for corrosion prediction, in particular, the issue of how to deal with organic acids and alkalinity including sampling analysis and interpretation.

• The theoretical background of pH calculation and water chemistry is introduced briefly.
• Current issues with water analyses and their interpretation for corrosion prediction are reviewed.
• The advantage and disadvantages of various pH calculation options with different water data inputs in the corrosion model are introduced.
• Different water sample analyses methods are reviewed
• Guidelines on interpreting lab data and approaches for calculating total alkalinity are provided for practical use.