Pitting corrosion inhibition

Effects of Alloy Composition on Pitting Corrosion Inhibition of Pitting Corrosion Crevice Corrosion... 

Nitrate ions have a special influence by inhibiting pitting corrosion in neutral and acid waters atU> [Eq. (2-50)] [48,52], corresponds to a second pitting potential and is designated the inhibition potential. The system belongs to group IV, with pitting corrosion at U U... 

Uhlig, H. H. and Gilman, 3. R., Inhibition of Pitting Corrosion of Stainless Steel 18/8 in Iron(III) Chloride Solutions by Nitrates , Z. Physik. Chem.,21/6, 127 (1964) C.A., 61,9231c Fisher, W. R., Pitting Corrosion, Especially of Titanium. 1 Corrosion Studies , Techn. Mill. 

The anions such as halogenides stimulate the active dissolution of zinc and tend to break down the passive film. Therefore, the effect of halogenide anions [267-270], thiocyanate [271], and sulfur-containing anions [272-274] in different media was studied. There are also anions that inhibit active dissolution and pitting corrosion, and this effect decreases in the... 

The problem with relying solely on anodic area corrosion inhibition is the risk of local film damage, which concentrates the corrosion current flow and permits a highly active anodic cell to be developed and causing accelerated corrosion to take place. This in turn leads to severe metal wastage, often in the form of deep pitting. 

It should be mentioned that passive layers are not protective in all environments. In the presence of so-called aggressive anions, passive layers may break down locally, which leads to the formation of corrosion pits. They grow with a high local dissolution current density into the metal substrate with a serious damage of the metal within very short time. In this sense halides and some pseudo halides like SCN are effective. Chloride is of particular interest due to its presence in many environments. Pitting corrosion starts usually above a critical potential, the so-called pitting potential /i]>j. In the presence of inhibitors an upper limit, the inhibition potential Ej is observed for some metals. Both critical potentials define the potential range in which passivity may break down due to localized corrosion as indicated in Fig. 1. 

The pitting corrosion of copper has been inhibited by injection of ferrous salt solution. Ferrous ion injection probably results in the formation of lepidrocrocite, FeO.OH, and provides protection. 

The investigations on corrosion and corrosion inhibition were carried out under the conditions of the oxidation experiments and also at elevated temperatures up to 523 K. The metallic samples were not pre-treated. On the surface of carbon steel St 1203 as well as high-grade steel 1.4541 without addition of an inhibitor corrosion and pitting can clearly be seen after the... 

A passive metal, which is subject to pitting corrosion beyond the pitting potential, Epit, in the presence of chloride ions, will be inhibited from pitting corrosion if an n-type oxide makes the electrode potential of the metal less positive than Epit. Furthermore, for a corroding metal in the active... 

E7.9. Pitting inhibitor effectiveness depends strongly on type and anion concentration. The thermodynamic (critical) activity, ai, required to inhibit pitting corrosion for a given activity of the aggressive anion is described by [13] ... 

Step of initiation of SCC [36], It has been reported that bound water, which occupies active sites for corrosion, initiates pitting corrosion [37]. Zhang et al. [38,39] suggested that the same model could be apphed to explain the inhibition and acceleration of anions [38] and cations [39] for the initiation of SCC. 

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