Corrosion of iron inhibition

Concentration Inhibition of iron corrosion in distilled water occurs only... 

Similar calculations have been carried out for the inhibition of iron corrosion in hydrochloric acid by Victoria blue which, according to Elze and Fischer (m) does not affect the Tafel slopes, but reduces both the anodic and cathodic partial reactions to a different degree. In this particular case 0q and 02 have to be adjusted by way of a trial and error calculation. 

Figure 10. Inhibition of iron corrosion by 2-butyne-l,4-diol in 6N HCl aerated...

Cao, R, Gu, R. and Tian, Z. (2002) Electrochemical and surface-enhanced Raman spectroscopy studies on inhibition of iron corrosion by benzotriazole. Langmuir, 18, 7609-7615. 

Many papers have been devoted to the inhibition of iron corrosion in acidic media by aromatic or acethylene compounds (Olen et al., 1962 Leroy, 1987 Srhiri and Ben Bachir, 1970 Benchekroun etal., 1985), by primary aliphatic amines and aminoalco-hols (Perbons and Rocchini, 1983 Mager-ramov et al., 1997 Bastidas et al., 1997), and by nonionic surfactants (Jian and Shon, 1985). The parameters influencing the inhibitory action of aliphatic amines and qua-... 

Aromatic sulfoxides are excellent inhibitors for iron corrosion in acidic media. Several studies have dealt with the inhibition of iron corrosion in H2SO4 using dibenzylsulf-oxide (DBSO). Trabanelli (1989) and Ohno et al. (1993) explained the inhibiting effect of DBSO by its conversion to sulfide on the electrode surface. 

Concentration. Inhibition of iron corrosion in distilled water occurs only when the anion concentration exceeds a critical value. At concentrations below the critical value, inhibitive anions may act aggressively and stimulate breakdown of the oxide films. Effective inhibitive anions have low critical concentrations for inhibition. A number of anions have been classified in order of their inhibitive power toward steel, judged from their critical inhibitive concentrations. The order of decreasing inhibitive efficiency is azide, ferri-cyanide, nitrite, chromate, benzoate, ferrocyanide, phosphate, tellurate, hydroxide, carbonate, chlorate, o-chlorbenzoate, bicarbonates fluoride, nitrate, and formate. 

Figure 5.1 Effect of oxygen concentration on corrosion of mild steel in slowly moving water containing 165 ppm CaCl2 48-hour test, 25°C. [Courtesy of H. H. Uhlig, D. N. Triadis, and M. Stern, Effect of Oxygen, Chlorides, and Calcium Ion on Corrosion Inhibition of Iron by Polyphosphates, J. Electrochem. Soc. 102, p. 60 (1955). Reprinted with permission by The Electrochemical Society, Inc. ]...

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 effects of inhibitive and aggressive anions on the corrosion of zinc are broadly similar to the effects observed with iron. Thus with increasing concentration, anions tend to promote corrosion but may give inhibition above a critical concentration Inhibition of zinc corrosion is somewhat... 

Cr, Br , I, which cause pitting attack, and anions which form soluble complexes with aluminium , e.g. citrate and tartrate, which cause general attack. Competitive effects , similar to those observed on iron, are observed in the action of mixtures of inhibitive anions and chloride ions on aluminium. The inhibition of aluminium corrosion by anions exhibits both an upper and a lower pH limit. The pH range for inhibition depends upon the nature of the anion . 

In general, paint adhesion and salt spray corrosion inhibition of iron phosphate coatings post-treated with polyvinylphenol derivatives have been equal to or superior to that obtained with chromate based systems. This has been the case particularly with many high solids paints. 

Using the HSAB principle, one can rationalize the corrosion inhibition of iron and aluminum by phosphate in which iron phosphate and aluminum phosphate are produced. Ferric and Al3+ are hard acids, and they react with phosphate, a hard inhibitor and give corrosion protection. Corrosion inhibition of Cu2+ and Zn2+ by amines can be rationalized by the formation of amine complexes of Cu2+ and Zn2+, and this is in accord with the principle that Cu2+ and Zn2+ are borderline acids reacting with amines which belong to borderline inhibitors. Corrosion protection of copper (soft acid) by mercapto-benzothiazole (soft inhibitor) is also in keeping with the HSAB principle. 

Already in 1952 the effectiveness of TcOj ions in aqueous solutions for the corrosion inhibition of iron and carbon steels was discovered [32.33]. A specimen of steel was efficiently protected against corrosion at temperatures of up to at least 250 "C in aerated distilled water containing 5-10 M TcOj, one-tenth of the concentration required for corrosion inhibition by CrO. The test specimen remained bright and unchanged in weight after being exposed for 20 years in the aqueous TCO4 solution at pH 6. To achieve inhibition under very corrosive conditions not more than 2.2 lO technetium atoms per cm- must be deposited on the surface of the specimen, about a tenth of a monolayer, ffowever. an inhibited specimen corroded at once when... 

Of course, the actual application of pertechnetate ions to corrosion inhibition of iron and carbon steels will obviously be a great problem because of the radioactivity of Tc, even in dilute solutions of TcO. A pertechnetate concentration of 5 10 M corresponds to a specific radioactivity of 84.15 pCi/l or 3.11 U/ Bq/1. Nevertheless, the corrosion inhibiting property of TcOj was proposed to be used in steam-generating nuclear reactors [42,43[-... 

Hoar Ci J found that in the corrosion inhibition of iron in hydrochloric acid by g-naphthoquinoline, the corrosion potential increases monotonically with increasing inhibitor concentration, while in the case of o-tolylthiourea one observes first a decrease of the corrosion potential followed by an increase at higher inhibitor concentrations. A similar predominant inhibition of the cathodic partial reaction at small inhibitor concentrations is exhibited also by phenylthiourea according to Kaesche. Furthermore, in the series of the thiourea derivatives one often finds corrosion acceleration at small concentrations, as for instance in the case of phenylthiourea at concentrations of 10- moles per liter. This appears to be due to a small cathodic decomposition of thiourea and its derivatives in the course of which hydrogen sulfide is formed. As is well known, hydrogen sulfide tends to accelerate corrosion, in particular the anodic partial reaction of dissolution of iron, which has been demonstrated independently by other authors (17). 

Khaled, K.F., K. Babic-Samardzija, and N. Hackerman, Theoretical study of the structural effects of polymethylene amines on corrosion inhibition of iron in acid solutions. Electrochimica Acta, 2005. 50(12) p. 2515-2520. 

Troquet, M., and Pagetti, J. (1983). Inhibition of metallic corrosion in an acid medium by means of phosphonium salts Zinc and iron. Werkst. Korros., 34(11), 557-562 (in German). 

Troquet, M. and Pagetti, J., Inhibition of Metallic Corrosion in an Acid Medium by Means of Phosphonium Salts Zinc and Iron, (in German) Werkstoffe und Kormsion, Vol. 34, No. 11, November 1983, pp. 557-562. 

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