Corrosion is a well-known threat for any metallic structure. An investigation conducted by the National Association of Corrosion Engineers (NACE) revealed that costs attributed to direct corrosion in the USA were USD $276B in 1998, which was equivalent to 3.1% of GDP (NACE 2002). The total cost of corrosion within Australia is at present estimated to be AUD $13B per year.
Since bronze was invented by ancient Chinese in 1700BC, the corrosion of metal has been a significant ongoing issue. The problem is aggravated with the advent of more chemically active iron & steel, which is widely utilised for structures in modern society. Understanding corrosion and corrosion control methods have become a serious topic for scientists and engineers around the globe. These problems can only be managed & resolved by a thorough understanding of their mechanisms. Corrosion is also recognised as a process safety issue in many industries. A proactive approach via best-practice engineering in Design, Installation, Production, Transportation & Operation, should be adopted to minimise failures and accidents caused by corrosion.
It is believed that successful corrosion management & control is always dependent on the following factors:
- Asset life cycle management;
- Understand fluid corrosivity;
- Monitor process conditions;
- Track and analyse operation and maintenance history.
There are always two fundamental strategies to combat corrosion: better corrosion resistant materials and better corrosion prevention practices. Stainless steel is a good example of the first strategy: The first corrosion resistant steel was not commercially available until 1914. Since then, they are widely used in corrosive environments with great success. Coating, Cathodic Protection, and Chemical Treatment are examples of the second strategy for combating corrosion. Various time-proven methods for the prevention and control of corrosion depend on the specific material to be protected and the specific corrosive environment.
Despite all of our endeavours, we must accept the fact that corrosion is a natural process and that metal structures will corrode in a favourable environment over time. Whilst it is doubtful we will never win the war against nature, we can, however, implement a systematic approach throughout the asset life cycle to minimum cost. Here is an overview of corrosion management. If detected early enough, some corrosion damage can be repaired. However, other damage may require a rotatable spare depending upon the nature and location of the damage. Corrosion control must be an ‘integrated approach’ as it must integrate corrosion detection, mitigation and inspection activities with the overall business direction, including Loss Production Opportunities (LPO) and Production Surveillance and Optimisation (PSO).