Abstract
In many service applications, excursions in solution chemistry, temporary loss of inhibitor, or transient increases in temperature may give rise to localized corrosion in an otherwise inhibited system. It is important to demonstrate that inhibition will be effective in retarding the rate of propagation of localized corrosion when normal conditions, appropriate to the prevention of general corrosion, are restored. To test this requirement, the use of a “pencil” type of artificial pit has been investigated using simple simulations of a cooling water and of an oil production formation water. The results demonstrate the effectiveness of this technique and show that nitrite, as an example of a cooling water inhibitor, can be effective in retarding the rate of propagation with the appropriate dosage. Tests in simulated oil production formation waters at 50°C demonstrated that an imidazoline-based inhibitor can decrease pit growth kinetics in nearly neutral carbon dioxide (CO2)-saturated solution but does not appear to be so effective with oxygen contamination of that solution or in mildly acidic CO2-saturated solution.
