The traditional Corrosion Inhibitor Efficiency Model has been reviewed and shown to have some failings particularly with respect to the design of new facilities. The problem of considering a single, deterministic corrosion rate has been discussed and the distribution of corrosion rates about a mean ( or modal ) value has been considered. The role of a corrosion inhibitor to not only reduce the mean corrosion rate but also decrease the spread of corrosion rates has been highlighted.
A Corrosion Inhibitor Availability Model has been introduced, the benefits of which are:
? A focus on the required corrosion rate.
? Removes focus from the mean corrosion rate only.
? Accounts for realistically achievable corrosion rates.
? Identifies the importance of the availability of corrosion inhibitor.
? Accounts for the interruption or the absence of inhibitor from time to time.
? Does not allow dangerously low corrosion allowances to be used.
The limitations on the use of corrosion inhibitors has been discussed and a Corrosion Inhibitor Risk Category has been introduced. Data from the Prudhoe Bay operation in Alaska is used to support the ideas discussed. Much of the discussion focuses on the design of new facilities. However, the approach is equally applicable to existing operations.
For many years the Corrosion Inhibitor Efficiency Model has been used to quantify the benefits of a corrosion
inhibitor treatment program when designing new pipelines and facilities. However, recently some operators have found the model to have some shortcomings. This paper discusses these and introduces the Corrosion Inhibitor Availability Model as an alternative approach. As part of the discussion, consideration is given to the benefits of using a distribution of corrosion rates about a mean value, rather than a single, deterministic corrosion rate. It is shown that the role of a corrosion inhibitor is not to only reduce the mean corrosion rate but also decrease the spread of corrosion rates.
Field data from Alaska is used to support the ideas discussed. Much of the discussion focuses on the design of new facilities. However, the approach is equally applicable to existing operations
