Corrosion protection cathodic inhibitors

EIS is the response of corrosion systems to ac excitations. It has been used in corrosion research to estimate corrosion rates or study the metal passivation, corrosion protection using inhibitors, sacrificial barrier properties, and polymer coating performance on metals. EIS only estimates polarization resistance. As with Hnear polarization, the corrosion current is calculated using the Stem-Geary equation for known values of the anodic and cathodic Tafel slopes. 

As a matter of fact, almost all of the above-mentioned materials are used in oil and gas industries, but the most common material that is used in bulk quantities is steel and its various types. The tonnage of other materials used is negligible compared to that of steel. Further, as it is well known that steel, in any form, is prone to corrosion, all steels used need to be protected by one or more methods of corrosion protection coatings, inhibitors, or cathodic protection. 

The extent of inhibition afforded to metals other than mild steel depends on the metal and the inhibitor see The Nature of the Metal, and Dissimilar Metals in Contact). The cathodic type of inhibitor is perhaps less susceptible than the anodic type to the nature of the metal. However, cathodic inhibitors are usually less efficient (although performing quite satisfactorily in many systems) in terms of reduction in corrosion rate, than are anodic inhibitors. The latter, when used in adequate concentrations, can often achieve 100% protection. 

Cathodic inhibitors reduce corrosion by rapidly polarizing the cathode. Examples of cathodic inhibitors are filming amines, magnesium salts, and calcium salts. In waters containing carbon dioxide, calcium carbonate precipitates (as discussed above) to form a protective film. 

Corrosion, the degradation of a material s properties or mass over time because of environmental effects, is a costly reality that effects every industry. A study issued by the Federal Highway Administration (FHWA) in 2002 conservatively estimates the annual direct cost of corrosion in all U.S. industry sectors at US 276 billion. Costs associated with corrosion include cathodic/anodic protection coatings inhibitors corrosion-resistant alloys and materials and maintenance, repair, and depreciation of equipment. Indirect costs, such as lost productivity, environmental or product contamination, planning and design, and lost opportunities, can easily outpace direct costs by factors of two or more. 

The terminology anodic and cathodic inhibitors is based on these functions. Anodic protection prevents or limits electron flow to the cathode area. Cathodic inhibitors generally reduce the corrosion rate by forming a barrier at the cathode thereby restricting the hydrogen ion or oxygen transport to the cathode surface. Tables 14.6 and 14.7 provide some information on common corrosion inhibitors. Specific corrosion control requirements are usually based on blends of two or more of the listed chemicals perhaps, in addition to chemicals to control scale formation and biological activity. 

In Chapter 10 the electrochemical nature of corrosion is discussed. Since corrosion of metals involves the passage of electric currents it is logical to adopt an electrical method to prevent corrosion. In Chapter 14 the use of both anodic and cathodic inhibitors (barriers) to prevent the flow of electrons is considered. It is possible to achieve similar protection by the use of electric currents. 

This definition excludes inhibitor films or other corrosion-protecting layers such as paint and so on, which have the same function as passive films but a different origin. Such films are formed from components in the electrolyte (inhibitors) or are deposited in a technical process (e.g. cathodic deposition of paint). 

The Uhlig methodology was used to determine the corrosion costs on the basis of the cost of corrosion protection products and services such as coatings, inhibitors, corrosion-resistant materials, and cathode protection. The total cost amounted to 2.5 trillion yen (US 9.2 billion). Paint and protective coatings accounted for nearly US 6.1 billion. Surface treatments and corrosion-resistant materials accounted for nearly two-thirds of the corrosion costs. Surface treatments and corrosion-resistant materials amounted to nearly one quarter and one-tenth of the costs, respectively. The remaining 5% of the cost was assigned to other corrosion control methods (Table 2.4). 

Performance of Stainless Steel Rebar in Concrete Corrosion protection of steel rebar can be achieved by (i) selection of corrosion-resistant steel (ii) use of coatings (iii) addition of corrosion inhibitors such as calcium nitrite to concrete mix (iv) addition of concrete sealers (iv) use of membranes (v) use of thicker concrete overlay (vi) cathodic protection. 

Established methods of protection include cathodic protection, coatings, addition of inhibitors to the concrete, or a combination of these methods. Coating the concrete and using corrosion inhibitors are the most common corrosion protection techniques. The use of corrosion inhibitors is more attractive because of its low cost and ease of application. Corrosion inhibitors can be added during mixing the... 

Underground pipelines are essential requirement of any developed country. Transportation of crude oil, gas, and many hydrocarbons are carried out through underground CCPs, as they are one of the safest modes of transportation, causing minimum disturbance to mankind. Since the material of construction of pipelines is steel, which is prone to severe corrosion, both from inside and outside, safety of pipelines depends upon a foolproof system of corrosion protection. All three major techniques of corrosion protection, namely, coatings, inhibitors, and cathodic protection, are used to protect pipelines. Protection of pipelines alone is not enough it is also important to monitor... 

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