Importance of Corrosion and Prevention

Materials technology is a very vital part of modern technology. Technological development is often limited by the properties of materials and knowledge about them. Some properties, such as those determining corrosion behaviour, are most difficult to map and to control.

In general, the development of modern society and industry has led to a stronger demand for engineers with specialized knowledge in corrosion. There are a number of reasons for this:

a) The application of new materials requires new corrosion knowledge.

b) Industrial production has led to pollution, acidification and increased corrosivity of water and the atmosphere.

c) Stronger materials, thinner cross-sections and more accurate calculation of dimensions make it relatively more expensive to add a corrosion allowance to the thickness.

d) The widespread use of welding has increased the number of corrosion problems.

e) The development of industrial sectors like nuclear power production and offshore oil and gas extraction has required stricter rules and control.

f) Considering the future, it should be noticed that most methods for alternative energy production will involve corrosion problems.

The cost of corrosion in industrialized countries has been estimated to be about 3– 4% of the gross national product [1.7, 1.8]. It has been further estimated that about 20% of this loss could have been saved by better use of existing knowledge in corrosion protection, design etc. In other words, there is a demand for applied research, education, information, transfer of knowledge and technology, and

technical development. Teaching, where considerable emphasis is placed on the connections between practical problems and basic scientific principles, is considered to be of vital importance (see Section 1.3).

The cost of corrosion is partly connected with the efforts to give structures an attractive appearance, it is partly the direct cost of replacement and maintenance and the simultaneous economic loss due to production interruptions, and it includes extra cost of using expensive materials and other measures for the prevention of corrosion and the loss or destruction of products.Besides the financial cost, a good deal of attention should be paid to safety risks and the pollution of the environment due to corrosion. Personnel injuries can occur due to the fracture of structures, the failure of pressure tanks and leakages in containers for poisonous, aggressive or inflammable liquids, for example. The extent of corrosion damage in the process industry can be exemplified: of the material failures recorded in the DuPont Company during a two-year period, 57% were corrosion failures and 43% were mechanical failures. In offshore oil and gas production, Statoil’s experience is that about half of the material failures are due to

corrosion and corrosion fatigue.The corrosion problems connected with oil production have been given much attention in many countries, not least those with extensive engagement in offshore oil

production. This seems reasonable when one considers the huge offshore installations which consist of non-resistant materials in contact with highly corrosive environments, in deep water and under conditions that make inspection and control difficult. It is evident that these problems represent a great challenge and require a high level of knowledge in corrosion technology. Many research projects have been

carried out to meet these challenges and requirements and considerable engineering activities have been established where careful attention is paid to modern, advanced methods for inspection, monitoring, control and calculation. Two examples of engineering improvements are dealt with below.

One of the first oilfields developed in the North Sea was Ekofisk. Up to the beginning of the 1980s, corrosion in the production tubing was the cause of 44% of all maintenance costs for “Greater Ekofisk” This maintenance cost due to corrosion amounted to the order of GBP 20 million during 1981–1982. In addition, the annual cost of inhibitors reached a maximum of about GBP 0.5 million in these years. From 1982–83, the maintenance cost has been reduced strongly by establishing a corrosion control programme calculated to cost approximately GBP 8

million.

Surface treatment in order to protect steel structures represents a large expense too. On the Norwegian continental shelf these expenses were about GBP 100 million annually until 1987–88. (This excludes the cost of preventing corrosion in process systems.) By means of increased know-how and conscious control by the oil companies, this amount was halved by 1994. A further reduction in cost can be obtained on the basis of life-cycle analyses and evaluation of the real needs for surface treatment on each part of the installations (selective maintenance) [1.11].