ABSTRACT

A new strategy has been applied successfully to pre-select corrosion inhibitors and short-list products to be considered by the operators. In particular the more comprehensive evaluation of the partitioning properties of the chemicals has improved the chances of successful application in the field. Some of these products have already been tested in the field to verify their effectiveness. The availability of suitable field corrosivity and monitoring methods has been a key success factor.

INTRODUCTION

Corrosion inhibition is one of the most commonly used methods for controlling corrosion of carbon steel equipment in oil and gas production, transportation, and processing. In recent years corrosion inhibition has become more and more common in our operations, even to protect carbon steel in relatively aggressive conditions 1. A large number of commercial corrosion inhibitors is available, and new products are being continuously introduced to handle more corrosive conditions and to meet more stringent environmental regulations.

Our laboratories have been involved repeatedly in selecting the best product from a long list of candidate products provided by the suppliers. The test procedures are described in our externally available report "Corrosion inhibitor testing and selection guidelines ''2. In reference 1, a total of 33 products from 10 suppliers were submitted for consideration for a pipeline project. This example is typical of the challenges facing the corrosion engineer who has to make a well-supported recommendation in a short time and with limited resources.

Unfortunately, the results of one project could rarely be used for another, because the tests were always carried out at very specific conditions. Hence, in spite of the commonality of the objectives of the test programs, the time and money invested was paid back by only one project. The time required to develop a shortlist of products for a specific application was often excessive, and final verification tests, e.g. flow loop tests to verify shear resistance or compatibility tests with other chemicals present in the system put the project schedule at risk.

In our role as consultants, we have to react quickly and keep an eye on future developments. Obviously, the above-described ad hoc approach does not allow us to fulfil this function very efficiently. In particular the need to stimulate the development of environmentally friendly ("green") products and the trend to apply inhibition in more aggressive conditions in terms of higher temperatures and shear will be key factors. To this end, it was decided in 1999 to develop a set of procedures to pre- select corrosion inhibitors for Standardized conditions, which are described in this paper. Additional more specific laboratory tests and field verification tests, recommended for critical applications, are described elsewhere.

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