Aluminium
Content
Protection of Metals, Vol. 37, No. 6, 2001, pp. 572–574. Translated from Zashchita Metallov, Vol. 37, No. 6, 2001, pp. 633–635. Original Russian Text Copyright © 2001 by Oshe, Saakiyan, Efremov.
Corrosion Behavior of Aluminum Alloys in the Presence of Hydrogen Sulfide
E. K. Oshe*, L. S. Saakiyan**, and A. P. Efremov**
* Institute of Physical Chemistry, Russian Academy of Sciences, Leninskii pr. 31, Moscow, 117915 Russia ** Gubkin State Academy of Oil and Gas, Leninskii pr. 65, Moscow, 117917 Russia
Received April 12, 1995
Abstract—The corrosion–electrochemical behavior of both carbon steel and aluminum alloys in hydrogen sulfide-bearing mineralized media is considered. An increase in the partial pressure of hydrogen sulfide aggravates the catastrophic breakdown of carbon steel, yet diminishes both the corrosion rate and the localization of corrosion attack on aluminum alloys. An investigation of the nature of the nonstoichiometry of surface oxide films on both carbon steel and aluminum alloys with the use of photoelectric-recombination method, revealed that the films fundamentally differ in semiconductive properties, according to which hydrogen sulfide can either promote or inhibit the corrosion. That is why hydrogen sulfide oppositely affects the corrosion–electrochemical behavior of aluminum alloys and carbon steels.
INTRODUCTION Aluminum alloys, by virtue of their intrinsic properties, oust structural steels from a lot of well-known spheres. Their low density, high specific strength (three times that of medium-carbon steel) and good compressibility; immunity to cold brittleness, sparking, salt crust and paraffin deposition, etc., are of interest to the oil– gas industry. An essential advantage of aluminum alloys is their insusceptibility to hydrogenation and hydrogen embrittlement. Hydrogen solubility in aluminum is too low to affect substantially the mechanical properties of aluminum alloys. They also highly outperform structural steels in corrosion resistance to H2S-containing media common to the oil–gas industry. In the presence of moist hydrogen sulfide, carbon- and low-alloyed-steels suffer severe electrochemical corrosion resulting in hydrogenation, embrittlement, and cracking. The presence of hydrogen sulfide in the electrolyte can accelerate corrosion of steel by an order of magnitude and terminate in a catastrophic breakdown of a gas–oil production equipment long before its normative service life [1, 2]. According to present views, hydrogen sulfide promotes the corrosion of steel through the formation of intermediate catalytic compounds. During anodic reaction, such intermediate complexes promote both the regeneration of hydrogen sulfide and the ionization of iron. Iron ions and dissolved hydrosulfides react to yield different FexSy sulfides depositing at the steel surface. If the H2S concentration is low, the sulfide film may be sufficiently tight and adherent to the metal and even exhibit some protective properties. With an increase in the concentration, the film becomes looser and less adherent to the metal, thus losing its protective properties, while the attendant growth of the electrode
potential in turn results in accelerating the anodic dissolution of iron. Moreover, surface hydrogen sulfides promote the penetration of cathodically discharging hydrogen into the steel. Hydrogen molecules forming at the traps of crystalline lattice increase the internal stresses of the metal. As a result, blisters form at the surface of mild steels, whereas stronger steels undergo embrittlement and cracking. In contrast, the same dissolved hydrogen sulfide inhibits rather than promotes the corrosion of aluminum and aluminum alloys in aqueous solutions [3, 4]. It enhances the protective properties of the oxide films and promotes their formation on juvenile aluminum surfaces. The foregoing dramatically shows up in a flow of electrolyte with suspended abrasive. Being introduced into such a flow, hydrogen sulfide elevates the free corrosion potential of a Ñ16T-alloy and almost halves the corrosion current. RESULTS AND DISCUSSION To investigate the effect of hydrogen sulfide on the corrosion rate of aluminum alloys more closely, we performed tests in an autoclave which enabled us to vary the partial pressure of H2S. An aqueous test solution contained 100 g/l NaCl, the temperature was 45°C; and the partial pressure of CO2 was 0.5 MPa. The partial pressure of H2S was varied from 0 to 1.5 MPa. The total gauge pressure in the working space was 5.0 MPa. Table 1 presents the results of 720-h-long testes. One can see that in the case of aluminum alloys, an increase in the partial pressure of hydrogen sulfide decreases the corrosion rate (rather than increases it, as would be in the case of steel).
0033-1732/01/3706-0572$25.00 © 2001 MAIK “Nauka /Interperiodica”
CORROSION BEHAVIOR OF ALUMINUM ALLOYS
573
Insofar as in practice, the corrosion effect of hydrogen sulfide may in turn be affected by other factors, we tested aluminum alloys, varying the temperature, the mineralization of the corrosive medium, and the partial pressure of H2S over wide limits. The tests were carried out in an autoclave in a biphase medium comprising petrol and water solution of NaCl in a ratio of 1 : 1, by applying a multivariable experimental design. The variable factors were the NaCl content (30, 105, and 180 g/l), the temperature (20, 70, and 120°C), and the partial pressure of H2S (0, 0.75, and 1.5 MPa). The total pressure was 10 MPa. We tested alloys of different alloying systems and production processes, namely, wrought alloys (Äåˆ Äå„6, and Ñ16í) and cast alloys (Äã9, Äã23, and Äã7). The alloying systems were selected in accordance with the classification of aluminum alloys by corrosion resistance [5]. By statistical treatment, we obtained correlation dependences which allow estimating the contribution of both the individual factors and their combinations to corrosion damage. For all the alloys under study, the regression equation takes the form: Y = a1 X 1 + a2 X 2 + a3 X 3 – b1 X 1 X 2 + b2 X 1 X 3 + b3 X 2 X 3 , where Y is the corrosion rate, X1 is the concentration of NaCl, X2 is the partial pressure of hydrogen sulfide, and X3 is the temperature. In the regression equations for all the alloys under study, the coefficients of the individual factors may be arranged in descending order as follows: a3 > a1 > a2 (see Table 2), which is to say that the temperature exerts primary control over the corrosion rate (which is generally known), whereas hydrogen sulfide and NaCl exert the weakest and intermediate effects, respectively. The X1X2 term appears in the equation with the minus sign, suggesting that hydrogen sulfide inhibits the corrosion more pronouncedly at low concentrations of NaCl. In evaluating the contribution of the combinations of the factors to corrosion, one can see that the temperature keeps its prevailing effect. In this case, the descending order of the coefficients is: b2 > b3 > b1 (see Table 2), that is, the combined effect of the temperature and the NaCl content (X1X3) is stronger than that of the temperature and the content of H2S (X2X3). Hence, the protective action of hydrogen sulfide suppresses the activating effect of the other factors, among them is the temperature, which individually activates corrosion most strongly. Such a correlation is characteristic of both wrought and cast alloys. Thus, promoting the corrosion of carbon steels, hydrogen sulfide protects aluminum alloys. In both the cases, its action increases with its partial pressure H2S. We also compared aluminum alloys with carbon steel from the viewpoint of the effect of their initial surface oxide films on their corrosion behavior in sulfidePROTECTION OF METALS Vol. 37 No. 6 2001
Table 1. The effect of the partial pressure of hydrogen sulfide on the corrosion rate of aluminum alloys (g/(m2 h)) Alloy Äå„3, Clad with ÄÑ35 Äå„3, Clad with ÄñÔÎ Ñ16í Clad with ÄÑ35 The partial pressure of H2S, MPa 0 0.2305 1.0 0.1843 1.0 0.1080 1.0 0.8 – – 0.1645 0.89 0.0880 0.85 1.5 0.1844 0.8 0.1523 0.83 0.0746 0.72
Table 2. The regression coefficients of both the individual factors and their combinations Alloy Äåˆ Äå„6 Ñ16í Äã9 Äã23 Äã7 a1 1.8 25.0 731.0 889.0 812.0 989.0 a2 a3 b1 b2 2.8 38.0 444.0 630.0 562.0 772.0 b3 0.9 18.0 80.0 352.0 170.0 498.0
0.5 1.9 –0.2 17.0 46.0 –16.0 19.0 983.0 –68.0 371.0 1013.0 –136.0 342.0 1231.0 –96.0 971.0 1571.0 –384.0
bearing mineralized water solutions. As demonstrated in [6, 7], an electroactive additive to an electrolyte can either inhibit or promote the corrosion depending on whether the nonstoichiometry of the surface oxide film is of oxygen or metallic nature. The opposite effects of hydrogen sulfide on the corrosion–electrochemical behavior of iron and aluminum are probably also attributable to a different nature of the nonstoichiometry of their surface oxide films. The nature of both the nonstoichiometry and the conductivity of the surface oxide film on an aluminum alloy immersed in a hydrogen-sulfide-containing solution was determined with a photoelectric-recombination method [8]. The method is based on an asymmetrical recombination of oxide’s electron–hole pairs photoexcited, by a pulse exposure of an electrode, in the fundamental bond of optical absorption of the surface oxide. When certain conditions are met, the method allows determining, from the sign and value of a photoresponse, the nature and extent of the oxide conductance and, hence its nonstoichiometry. The specimens to be studied were mechanically polished and exposed for 10 days either to distilled water (a reference specimen) or hydrogen-sulfide water (3.0 g/l). The surface oxides of both the specimens had a p-type conductance and contained excess oxygen. Hydrogen sulfide molecules tend to act as an electron
574
OSHE et al.
donor [9]. When interacting with a p-oxide, molecules of hydrogen sulfide or its dissociation products decrease the equilibrium concentration of majority carriers (holes). It is known that the majority carriers directly participate in redox reactions at the surface of wide-zone semiconductive oxides [8]. As a response to either a decrease or an increase in their concentration one observes the increase or the decrease, respectively, in both transport and kinetic restrictions imposed on reactions involving the oxide phase. Surface oxide films on iron and carbon steels in electrolyte solutions with a pH of more than 2.5 to 3.0 have n-type conductance and contain excess iron [10, 11]. Interaction of hydrogen sulfide (electron donor) with such oxides increases the concentration of their majority carriers (electrons) and promotes the corrosion. The effect of chloride ions on aluminum alloys in hydrogen sulfide-bearing media is associated with the breakdown of oxide film. The damage originates at sites with the minimal activation energy of the process. These may be local accumulations of nonstoichiometric defects dominating in aluminum oxide, namely cationic vacancies, at sites where dislocations or grain boundaries emerge at the oxide surface. At these sites, because of disruptions in the structure, the aluminum– oxygen atomic bond is weakened, which is favorable to the effective substitution of chloride-ions for oxygenions. Conceivably, dissolved hydrogen sulfide can heal the disruptions in the structure of the oxide film through a partial fixation of the ionic bonds of aluminum atoms within [AlO3S] tetrahedrons. Because of this, in mineralized media conducive to local corrosion of aluminum alloys, the presence of hydrogen sulfide may mitigate the localized corrosion attack. In such a case, an increase in the partial pressure of hydrogen sulfide is favorable to healing the surface centers of local breakdown and making corrosion uniform.
CONCLUSIONS In mineralized water solutions, hydrogen sulfide, promoting corrosion of carbon steel, inhibits corrosion of aluminum alloys; the higher its partial pressure the stronger the effects. Antipodal corrosion–electrochemical behavior of carbon steel and aluminum alloys in hydrogen sulfidebearing media correlates with the fundamental difference between the semiconductive properties of their oxide films, according to which hydrogen sulfide either promote or inhibit the corrosion, respectively. REFERENCES
1. Saakiyan, L.S. and Efremov, A.P., Zashchita neftegazopromyslovogo oborudovaniya ot korrozii (Corrosion Protection of Oil and Gas Equipment), Moscow: Nedra, 1982. 2. Shreider, A.V., Shparber, I.S., and Archakov, Yu.I., Vliyanie vodoroda na khimicheskoe i neftyanoe oborudovanie (Influence of Hydrogen on Chemical and Oil Equipment), Moscow: Mashinostroenie, 1976. 3. Saakiyan, L.S. and Zubkova, L.F., Neft. Prom-st’, Ser. Korroz. Zashch. Neftedobyvayushch. Prom-sti, 1972, no. 7, p. 15. 4. Saakiyan, L.S., Soboleva, I.A., and Shmuilovich, M.S., Zashch. Met., 1972, vol. 18, no. 5, p. 616. 5. Sinyavskii, V.S., Val’kov, V.D., and Budov, G.M., Korroziya i zashchita alyuminievykh splavov (Corrosion and Protection of Aluminum Alloys), Moscow: Metallurgiya, 1979. 6. Oshe, E.K. and Kryakovskaya, N.Yu., Zashch. Met., 1983, vol. 29, no. 3, p. 393. 7. Oshe, E.K., Sov. Sci. Rev., B, Chem. Rev., 1987, vol. 8, p. 219. 8. Oshe, E.K. and Rozenfel’d, I.L., Itogi Nauki Tekh., Ser.: Korroz. Zashch. Korroz., M.: VINITI, 1978, vol. 7, p. 111. 9. Vartanyan, A.T., Molekulyarnaya fotonika (Molecular Photonics), Leningrad: Nauka, 1970, p. 372. 10. Oshe, E.K., Extended Abstract of the Fourth JapanUSSR Corrosion Seminar, Tokyo, 1985, p. 55. 11. Oshe, E.K., Elektrokhimiya, 1994, vol. 30, no. 4, p. 499.
PROTECTION OF METALS
Vol. 37
No. 6
2001
Corrosion Behavior of Aluminum Alloys in the Presence of Hydrogen Sulfide
E. K. Oshe*, L. S. Saakiyan**, and A. P. Efremov**
* Institute of Physical Chemistry, Russian Academy of Sciences, Leninskii pr. 31, Moscow, 117915 Russia ** Gubkin State Academy of Oil and Gas, Leninskii pr. 65, Moscow, 117917 Russia
Received April 12, 1995
Abstract—The corrosion–electrochemical behavior of both carbon steel and aluminum alloys in hydrogen sulfide-bearing mineralized media is considered. An increase in the partial pressure of hydrogen sulfide aggravates the catastrophic breakdown of carbon steel, yet diminishes both the corrosion rate and the localization of corrosion attack on aluminum alloys. An investigation of the nature of the nonstoichiometry of surface oxide films on both carbon steel and aluminum alloys with the use of photoelectric-recombination method, revealed that the films fundamentally differ in semiconductive properties, according to which hydrogen sulfide can either promote or inhibit the corrosion. That is why hydrogen sulfide oppositely affects the corrosion–electrochemical behavior of aluminum alloys and carbon steels.
INTRODUCTION Aluminum alloys, by virtue of their intrinsic properties, oust structural steels from a lot of well-known spheres. Their low density, high specific strength (three times that of medium-carbon steel) and good compressibility; immunity to cold brittleness, sparking, salt crust and paraffin deposition, etc., are of interest to the oil– gas industry. An essential advantage of aluminum alloys is their insusceptibility to hydrogenation and hydrogen embrittlement. Hydrogen solubility in aluminum is too low to affect substantially the mechanical properties of aluminum alloys. They also highly outperform structural steels in corrosion resistance to H2S-containing media common to the oil–gas industry. In the presence of moist hydrogen sulfide, carbon- and low-alloyed-steels suffer severe electrochemical corrosion resulting in hydrogenation, embrittlement, and cracking. The presence of hydrogen sulfide in the electrolyte can accelerate corrosion of steel by an order of magnitude and terminate in a catastrophic breakdown of a gas–oil production equipment long before its normative service life [1, 2]. According to present views, hydrogen sulfide promotes the corrosion of steel through the formation of intermediate catalytic compounds. During anodic reaction, such intermediate complexes promote both the regeneration of hydrogen sulfide and the ionization of iron. Iron ions and dissolved hydrosulfides react to yield different FexSy sulfides depositing at the steel surface. If the H2S concentration is low, the sulfide film may be sufficiently tight and adherent to the metal and even exhibit some protective properties. With an increase in the concentration, the film becomes looser and less adherent to the metal, thus losing its protective properties, while the attendant growth of the electrode
potential in turn results in accelerating the anodic dissolution of iron. Moreover, surface hydrogen sulfides promote the penetration of cathodically discharging hydrogen into the steel. Hydrogen molecules forming at the traps of crystalline lattice increase the internal stresses of the metal. As a result, blisters form at the surface of mild steels, whereas stronger steels undergo embrittlement and cracking. In contrast, the same dissolved hydrogen sulfide inhibits rather than promotes the corrosion of aluminum and aluminum alloys in aqueous solutions [3, 4]. It enhances the protective properties of the oxide films and promotes their formation on juvenile aluminum surfaces. The foregoing dramatically shows up in a flow of electrolyte with suspended abrasive. Being introduced into such a flow, hydrogen sulfide elevates the free corrosion potential of a Ñ16T-alloy and almost halves the corrosion current. RESULTS AND DISCUSSION To investigate the effect of hydrogen sulfide on the corrosion rate of aluminum alloys more closely, we performed tests in an autoclave which enabled us to vary the partial pressure of H2S. An aqueous test solution contained 100 g/l NaCl, the temperature was 45°C; and the partial pressure of CO2 was 0.5 MPa. The partial pressure of H2S was varied from 0 to 1.5 MPa. The total gauge pressure in the working space was 5.0 MPa. Table 1 presents the results of 720-h-long testes. One can see that in the case of aluminum alloys, an increase in the partial pressure of hydrogen sulfide decreases the corrosion rate (rather than increases it, as would be in the case of steel).
0033-1732/01/3706-0572$25.00 © 2001 MAIK “Nauka /Interperiodica”
CORROSION BEHAVIOR OF ALUMINUM ALLOYS
573
Insofar as in practice, the corrosion effect of hydrogen sulfide may in turn be affected by other factors, we tested aluminum alloys, varying the temperature, the mineralization of the corrosive medium, and the partial pressure of H2S over wide limits. The tests were carried out in an autoclave in a biphase medium comprising petrol and water solution of NaCl in a ratio of 1 : 1, by applying a multivariable experimental design. The variable factors were the NaCl content (30, 105, and 180 g/l), the temperature (20, 70, and 120°C), and the partial pressure of H2S (0, 0.75, and 1.5 MPa). The total pressure was 10 MPa. We tested alloys of different alloying systems and production processes, namely, wrought alloys (Äåˆ Äå„6, and Ñ16í) and cast alloys (Äã9, Äã23, and Äã7). The alloying systems were selected in accordance with the classification of aluminum alloys by corrosion resistance [5]. By statistical treatment, we obtained correlation dependences which allow estimating the contribution of both the individual factors and their combinations to corrosion damage. For all the alloys under study, the regression equation takes the form: Y = a1 X 1 + a2 X 2 + a3 X 3 – b1 X 1 X 2 + b2 X 1 X 3 + b3 X 2 X 3 , where Y is the corrosion rate, X1 is the concentration of NaCl, X2 is the partial pressure of hydrogen sulfide, and X3 is the temperature. In the regression equations for all the alloys under study, the coefficients of the individual factors may be arranged in descending order as follows: a3 > a1 > a2 (see Table 2), which is to say that the temperature exerts primary control over the corrosion rate (which is generally known), whereas hydrogen sulfide and NaCl exert the weakest and intermediate effects, respectively. The X1X2 term appears in the equation with the minus sign, suggesting that hydrogen sulfide inhibits the corrosion more pronouncedly at low concentrations of NaCl. In evaluating the contribution of the combinations of the factors to corrosion, one can see that the temperature keeps its prevailing effect. In this case, the descending order of the coefficients is: b2 > b3 > b1 (see Table 2), that is, the combined effect of the temperature and the NaCl content (X1X3) is stronger than that of the temperature and the content of H2S (X2X3). Hence, the protective action of hydrogen sulfide suppresses the activating effect of the other factors, among them is the temperature, which individually activates corrosion most strongly. Such a correlation is characteristic of both wrought and cast alloys. Thus, promoting the corrosion of carbon steels, hydrogen sulfide protects aluminum alloys. In both the cases, its action increases with its partial pressure H2S. We also compared aluminum alloys with carbon steel from the viewpoint of the effect of their initial surface oxide films on their corrosion behavior in sulfidePROTECTION OF METALS Vol. 37 No. 6 2001
Table 1. The effect of the partial pressure of hydrogen sulfide on the corrosion rate of aluminum alloys (g/(m2 h)) Alloy Äå„3, Clad with ÄÑ35 Äå„3, Clad with ÄñÔÎ Ñ16í Clad with ÄÑ35 The partial pressure of H2S, MPa 0 0.2305 1.0 0.1843 1.0 0.1080 1.0 0.8 – – 0.1645 0.89 0.0880 0.85 1.5 0.1844 0.8 0.1523 0.83 0.0746 0.72
Table 2. The regression coefficients of both the individual factors and their combinations Alloy Äåˆ Äå„6 Ñ16í Äã9 Äã23 Äã7 a1 1.8 25.0 731.0 889.0 812.0 989.0 a2 a3 b1 b2 2.8 38.0 444.0 630.0 562.0 772.0 b3 0.9 18.0 80.0 352.0 170.0 498.0
0.5 1.9 –0.2 17.0 46.0 –16.0 19.0 983.0 –68.0 371.0 1013.0 –136.0 342.0 1231.0 –96.0 971.0 1571.0 –384.0
bearing mineralized water solutions. As demonstrated in [6, 7], an electroactive additive to an electrolyte can either inhibit or promote the corrosion depending on whether the nonstoichiometry of the surface oxide film is of oxygen or metallic nature. The opposite effects of hydrogen sulfide on the corrosion–electrochemical behavior of iron and aluminum are probably also attributable to a different nature of the nonstoichiometry of their surface oxide films. The nature of both the nonstoichiometry and the conductivity of the surface oxide film on an aluminum alloy immersed in a hydrogen-sulfide-containing solution was determined with a photoelectric-recombination method [8]. The method is based on an asymmetrical recombination of oxide’s electron–hole pairs photoexcited, by a pulse exposure of an electrode, in the fundamental bond of optical absorption of the surface oxide. When certain conditions are met, the method allows determining, from the sign and value of a photoresponse, the nature and extent of the oxide conductance and, hence its nonstoichiometry. The specimens to be studied were mechanically polished and exposed for 10 days either to distilled water (a reference specimen) or hydrogen-sulfide water (3.0 g/l). The surface oxides of both the specimens had a p-type conductance and contained excess oxygen. Hydrogen sulfide molecules tend to act as an electron
574
OSHE et al.
donor [9]. When interacting with a p-oxide, molecules of hydrogen sulfide or its dissociation products decrease the equilibrium concentration of majority carriers (holes). It is known that the majority carriers directly participate in redox reactions at the surface of wide-zone semiconductive oxides [8]. As a response to either a decrease or an increase in their concentration one observes the increase or the decrease, respectively, in both transport and kinetic restrictions imposed on reactions involving the oxide phase. Surface oxide films on iron and carbon steels in electrolyte solutions with a pH of more than 2.5 to 3.0 have n-type conductance and contain excess iron [10, 11]. Interaction of hydrogen sulfide (electron donor) with such oxides increases the concentration of their majority carriers (electrons) and promotes the corrosion. The effect of chloride ions on aluminum alloys in hydrogen sulfide-bearing media is associated with the breakdown of oxide film. The damage originates at sites with the minimal activation energy of the process. These may be local accumulations of nonstoichiometric defects dominating in aluminum oxide, namely cationic vacancies, at sites where dislocations or grain boundaries emerge at the oxide surface. At these sites, because of disruptions in the structure, the aluminum– oxygen atomic bond is weakened, which is favorable to the effective substitution of chloride-ions for oxygenions. Conceivably, dissolved hydrogen sulfide can heal the disruptions in the structure of the oxide film through a partial fixation of the ionic bonds of aluminum atoms within [AlO3S] tetrahedrons. Because of this, in mineralized media conducive to local corrosion of aluminum alloys, the presence of hydrogen sulfide may mitigate the localized corrosion attack. In such a case, an increase in the partial pressure of hydrogen sulfide is favorable to healing the surface centers of local breakdown and making corrosion uniform.
CONCLUSIONS In mineralized water solutions, hydrogen sulfide, promoting corrosion of carbon steel, inhibits corrosion of aluminum alloys; the higher its partial pressure the stronger the effects. Antipodal corrosion–electrochemical behavior of carbon steel and aluminum alloys in hydrogen sulfidebearing media correlates with the fundamental difference between the semiconductive properties of their oxide films, according to which hydrogen sulfide either promote or inhibit the corrosion, respectively. REFERENCES
1. Saakiyan, L.S. and Efremov, A.P., Zashchita neftegazopromyslovogo oborudovaniya ot korrozii (Corrosion Protection of Oil and Gas Equipment), Moscow: Nedra, 1982. 2. Shreider, A.V., Shparber, I.S., and Archakov, Yu.I., Vliyanie vodoroda na khimicheskoe i neftyanoe oborudovanie (Influence of Hydrogen on Chemical and Oil Equipment), Moscow: Mashinostroenie, 1976. 3. Saakiyan, L.S. and Zubkova, L.F., Neft. Prom-st’, Ser. Korroz. Zashch. Neftedobyvayushch. Prom-sti, 1972, no. 7, p. 15. 4. Saakiyan, L.S., Soboleva, I.A., and Shmuilovich, M.S., Zashch. Met., 1972, vol. 18, no. 5, p. 616. 5. Sinyavskii, V.S., Val’kov, V.D., and Budov, G.M., Korroziya i zashchita alyuminievykh splavov (Corrosion and Protection of Aluminum Alloys), Moscow: Metallurgiya, 1979. 6. Oshe, E.K. and Kryakovskaya, N.Yu., Zashch. Met., 1983, vol. 29, no. 3, p. 393. 7. Oshe, E.K., Sov. Sci. Rev., B, Chem. Rev., 1987, vol. 8, p. 219. 8. Oshe, E.K. and Rozenfel’d, I.L., Itogi Nauki Tekh., Ser.: Korroz. Zashch. Korroz., M.: VINITI, 1978, vol. 7, p. 111. 9. Vartanyan, A.T., Molekulyarnaya fotonika (Molecular Photonics), Leningrad: Nauka, 1970, p. 372. 10. Oshe, E.K., Extended Abstract of the Fourth JapanUSSR Corrosion Seminar, Tokyo, 1985, p. 55. 11. Oshe, E.K., Elektrokhimiya, 1994, vol. 30, no. 4, p. 499.
PROTECTION OF METALS
Vol. 37
No. 6
2001
