Corrosion Policy Decision Making. Группа авторов

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Figure 2.17 Some examples of paint application problems. Rusting on primer due to thin primer layer (a). Running of paint and settling of dirt due to adjacent blasting operation (b).

      Many paint defects are mainly related to the method of their application. The wrong choice of hardener and thinner for paints, incorrect mixing of paint components, and wrong choice of different layers of a paint system are the most common causes of complication in paint application. Accuracy at the important points in the catalog can cut problems. Lifting, orange peel, overspray, pinholes, spatter coat, etc. are some of the complications that may occur due to these problems [7].

      Excessive hot or cold temperature of the substrate, high humidity, dust, and local pollution are other factors that may cause complications during paint application. Adherence to implementation instructions greatly reduces these problems. Complications such as amine blushing, blushing, holidays, rusting, etc. are observed in these conditions [7].

Inadequate regulation of paint viscosity and spraying pressure in airless spraying, as well as inadequate air‐to‐paint ratio in air spraying methods are other causes of complications during application. These factors lead to difficulty in achieving the right thickness as well as complications such as sagging and running, etc.

      2.2.5.9 Inspection and Management

Industrial paint inspection plays an important role in the useful life of paints and paint systems. Unfortunately, in certain circumstances, surface preparation and paint application is performed without the necessary care by inspectors. For example, for problems referred to in Figure 2.18, the paint was applied only on visible sections. In addition, the primer was applied to the previous existing paint, which is another gross mistake of inspection.

      On the other hand, a number of refinery project managers have no technical approach to the issue of paints and some of them consider it as one of the last priorities. Unfortunately, sometimes the project manager tries to compensate for the delay in completing the project by reducing the surface preparation and paint application time, and orders for increasing the speed of the paint operations.

Paint is very important as the most common way to prevent corrosion. It also gives beauty to the facilities and will give the workers a sense of security and safety while doing their work. Lack of attention to the problems of paint leads to the rapid development of damage, especially in chemical and marine facilities that are more likely to exhibit paint problems. See some examples in Figure 2.19. In this comparison, the intervals of periodic visits were only two years.

Figure 2.18 Weak inspection and management.

Full documentation of the operation inspection can significantly reduce paint defects during the service life of the equipment. These documents show compliance with the standards. They show precision at choosing the right paint systems, performing the correct surface preparation, and good application. So, attention paid to proper instructions for the items listed in Figure 2.20 is essential.

Figure 2.19 Rapid development of damage, especially in chemical and marine facilities that are more likely to exhibit paint problems. Defects developed during two years. Documented at May 2009 (left). Documented at October 2011 (right).

Figure 2.20 Effective parameters on paint useful lifespan.

2.3 Conclusion

      Science of corrosion is based on understanding three main elements: what metal liberates electrons (thus becomes an anode and is consumed), which material takes electron (and becomes a cathode), and what fluid ions can move through easily. It follows, then, anything that can interrupt one or all of these elements is highly likely to affect corrosion and control it. If, for example, paint (more correctively, coating) is applied, then anode and cathode will not see each other or anode–cathode will be isolated from the external electrolyte; the former will not allow electron transfer and the latter will not allow ion exchange.

In this chapter, three main methods for corrosion prediction (SHE, Galvanic series, and Pourbaix doagrams) as well as categorizing five technical managements of corrosion have been briefly explained. In addition to a short description of each of the five categories, a rather detailed СКАЧАТЬ