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Corrosion Policy Decision Making


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selection (change and/or modification of design including change/upgrading of materials).

      2 Chemical treatment; use of various kinds of corrosion inhibitors (anodic inhibitors, cathodic inhibitors and mixed effect inhibitors, biocides either as oxidizing biocides or non‐oxidizing biocides).

      3 Electrical treatment (the most noticeable example in this context is cathodic protection).

      4 Mechanical treatment (pigging).

      5 Physical treatment (paints/coatings).

      Below we will briefly review these five treatment strategies. Once again, we should remind our readers that neither this chapter nor the book itself is about teaching corrosion science and the electrochemistry behind it in the way that many famous handbooks and textbooks do. Our main focus here is on knowing as much necessary for an engineer who happens to become responsible for developing a CM strategy and who may need to know some basic, important elements of the science of corrosion when trying to differentiate between CM various models. As we have described in full in Chapter 3 under the title of “Smart Corrosion Management Elements,” having an efficient, realistic, smart model for CM is an integral part of any strategy that seriously considers management of corrosion.

      2.2.1 Design Modification‐change/Materials Selection

      Contrary to what many engineers and operators may think, the as‐is design of assets is not the last word when it comes to CM of the asset. In fact, many factors during fabrication, welding, coating, testing, and operation may become the points at which corrosion can be invited. For instance, it is usually recommended to use continuous welding instead of spot welding to avoid problems such as moisture entrance, or having as few branches as possible in a pipeline to avoid stagnation points. In addition, it is highly likely that MIC problems can occur in post‐hydrostatic testing of pipelines, which is mainly applied to test the welding strength (contrary to pneumatic test which is essentially a leak test, hydrotest is both a strength and leak test).

      Yet another issue that may arise is to have formed galvanic cells by joining two metals that each can have different electrochemical properties (such as welding together the same metals with and without coating, or coupling dissimilar metals to each other so that in addition to creating a potential difference, anode/cathode area ratios less than one will be created). Operation conditions may lead into initiation and development of MIC in the asset, an example can be seen for example, in underground firewater rings or within reverse osmosis membranes systems. Examples are numerous.

      The policy is that before opting for design change‐modification/materials selection, do a thorough feasibility study to compare this option with the economy and possible outcome with the other four options (when applicable), and then decide if you want to continue with it or leave it, either temporarily or permanently.

Schematic illustration of materials selection chart for upstream exploration oil and gas industry.

      The issue will even become more considerable for projects that are being carried out in countries whose currency is not US dollars. When translated into their national currency, the imposed cost may become more eye catching, rendering it more likely to get negative responses to finance a materials selection option. Therefore, it is of vital importance to convince the management not only in terms of corrosion treatment‐related terms but also in terms of the service life extension via an economic analysis such as life cycle cost analysis (we have briefly explained this and other models in Chapter 3 [Smart Corrosion Management Elements] and in more details related to economy in Chapter 4 [A Short Review of Some Fundamental Principles of Economics]).

Schematic illustration of carbon steel price fluctuations with an average price of $0.5027/Ib (top).