Corrosion protection studies

In general, the addition of inhibitors to sol-gel systems provides additional corrosion protection of metal. Khramov et al studied the corrosion protection properties of hybrid sol-gel films deposited on aluminium alloy with different incorporated organic inhibitors such as mercaptobenzothiazole and mercaptobenzimidazole, mercaptobenzimidazolesulfonate and thiosalicylic acid (Khramov et al, 2004, 2005). Corrosion protection studied by localized methods of analysis such as SVET shows low ionic currents at the sites with artificial defects, which is attributed to active corrosion protection. An improvement of the corrosion protection has been also noticed for bis-silane films containing... 

A large number of studies concerned witli tliiol-tenninated molecules has been directed at tire preparation of tailored organic surfaces, since tlieir importance has been steadily increasing in various applications. Films of o> functionalized alkanetliiols have facilitated fundamental studies of interfacial phenomena, such as adhesion [190, 191], corrosion protection [192], electrochemistry [193], wetting [194], protein adsorjDtion [195, 196] or molecular recognition [197, 198, 199, 200 and 201] to mention only a few. 

The corrosion protection provided by phosphate coatings without a sealing treatment is of a low order their value when sealed is considerably greater. Unsealed corrosion tests are therefore of little value except perhaps for studying porosity or efficiency of coatings destined to be sealed only with oil. 

From experience in metalworking applications it is known that ether carboxylates may improve the existing corrosion protection of formulations [66]. From pKj studies described by Aalbers [49], an internal neutralization of the ether carboxylate micelles can be concluded resulting in less anionic character than, for example, alkyl sulfates therefore also combination with quats are possible without any problem. 

A word of caution Metals, materials in general, chemicals used to study metals in the laboratory, chemicals used for corrosion protection, and essentially any chemicals should be (1) used in compliance with all applicable codes, laws, and regulations (2) handled by trained and experienced individuals in keeping with workmanlike environmental and safety standards and (3) disposed only using allowable methods and in allowable quantities. 

Yu Runlan, Qiu Guanzhou, Hu Yuehua, Qin Wenqing, 2004g. The corrosive electrochemical study of marmatite. Journal of Chinese Society For Corrosion and Protection, 24(4) 226-229... 

Surface chemical characterization of the passivation layer on the Al surface has been performed mainly via XPS, and the interpretation of results generated by various researchers still remains controversial. Because salt anions with active fluorine (LiPFe, LiAsFe, and LiBF4) are able to form stable surface layers on Al and protect it from corrosion, early studies had suggested that fluoride species such as LiF and AIF3 are crucial to the protection. 

Polymeric materials are widely used to control the corrosion of metals, both to maintain appearance and to prevent loss of structural integrity. In this chapter, the fundamentals of metallic corrosion are briefly reviewed. Methods of studying corrosion, and of evaluating the performance of polymeric materials used in corrosion protection, are outlined. Factors that influence the corrosion protective perfoi iance of polymeric materials are discussed, and some of the research needs and important unsolved problems are highlighted. 

Electrochemical Characterization Technloues. Since corrosion Is an electrochemical process, It Is not surprising that a considerable amount of work has been reported over the years on electrical and electrochemical techniques for the study of the corrosion process. Leldhelser Ql.) and Szauer (12.> 11) have provided good reviews of the principal techniques. Walter has recently provided a review of DC electrochemical tests for painted metals (14). Both AC and DC methods have been employed to study a variety of Issues related to corrosion and corrosion protection. DC techniques are especially useful for studying substrate processes, while AC impedance techniques are most useful for studying processes relating to coated substrates and the performance of coatings. 

A related but little studied area of adhesion and corrosion protection involves the chemical effects of metal substrates on coatings and other polymeric materials and conversely of polymeric materials on metals. In the curing of certain air-oxidizing coatings on steel, for example, reduction of ferric to ferrous species in the surface metal oxide, substantial thinning of the oxide, and oxidation of the coating material have been reported to occur in the interfacial... 

Systems. Corrosion is usually studied in an isolated fashion in the laboratory, but in practice is clearly the result of interacting systems in the environment. Studies need to be conducted on the way in which the component parts of corroding systems Interact under actual environmental conditions, and on the way in which the components of the environment interact with the total corroding system. This would suggest not only design work for corrosion protection systems, but also additional work on the sensing and monitoring of corrosion in real hostile environments. 

Fourier transform infrared reflection-absorption spectroscopy (FT-IFRAS) is applied to the study of corrosion protection of copper by an organic coating. Poly-N-vinyliroidazole (PVI(D) and poly-4(5)-vinylimidazole (PVI(4)) are demonstrated to be effective new polymeric anti-corrosion agents for copper at elevated temperatures. Oxidation of copper is suppressed even at 400° C. PVI(1) and PVI(4) are more effective anti-oxidants than the most commonly used corrosion inhibitors, benzotriazole and undecyllmldazole, at elevated temperatures. These new polymeric agents are water soluble and easy to treat the metal surface. 

As stated, the capability of plasma deposits to reduce the access of water to corrosion-sensitive surfaces may be an important motivation for their application in corrosion protection. In order to study this property, Kapton polyimide film was selected as the substrate because of its high inherent permeability to water and its ability to resist elevated temperatures. The response of Kapton film overcoated by PPHMDSO to the permeation of water vapor is shown in Fig. 1. Clearly, the presence of the organo-silicone plasma film greatly reduces water permeation. The magnitude of the effect is much enhanced when plasma polymers are produced at high T and p. 

Metals such as aluminium, steel, and titanium are the primary adherends used for adhesively bonded structure. They are never bonded directly to a polymeric adhesive, however. A protective oxide, either naturally occurring or created on the metal surface either through a chemical etching or anodization technique is provided for corrosion protection. The resultant oxide has a morphology distinct from the bulk and a surface chemistry dependent on the conditions used to form the oxide 39). Studies on various aluminum alloy compositions show that while the oxide composition is invariant with bulk composition, the oxide surface contains chemical species that are characteristic of the base alloy and the anodization bath40 42). 

Provides abstracts of worldwide research on design and performance of mechanical draft and natural draft wet, dry, and dry-wet combination cooling towers. Abstracts cover studies on size reduction, corrosion protection, and economic optimization of cooling towers primarily used with nuclear power plants and fossil fuel power plants. Also covered are abstracts which pertain to cooling towers used in waste-water treatment. It contains 305 abstracts, 65 of which are new entries to the previous edition. 

Two recent studies have used surface techniques to examine the protective layers formed in various oxidation conditions and related the nature of the oxide to the corrosion rates in specific environments. Hultquist and Leygraf (43, 44) have examined crevice corrosion resistance in a NaCl solution at room temperatures while Baer (45) has looked at higher temperature (800°C) air oxidation. Oxygen potential, or partial pressure, is an important parameter in both studies where it was found that controlled oxidation can tailor the Cr profile in the alloy and surface oxide for maximum corrosion protection. Specific goals in each experiment were oxide characterization and comparison to corrosion rates... 

Recently, the mechanism of corrosion protection by soluble chromate inhibitors has been the subject of active research, which has attempted to understand and replicate its inhibiting functions with less toxic chemical substances. In this section, some recent findings on chromate corrosion inhibition are reviewed, particularly as they pertain to corrosion of light metals, with a focus on the use of techniques that are useful for studying mechanisms of inhibition. 

In addition to the organic compounds, waste water contains dissolved salts. This causes severe corrosion problems under conditions of operation in the near-critical region of water. The corrodibility of different materials in contact with waste water and oxidizing agents was investigated at temperatures up to 573 K and pressures up to 15 MPa. Furthermore, the applicability of appropriate inhibitors for corrosion protection was studied under mentioned conditions of wet oxidation. 

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