ISSN 1068364X, Coke and Chemistry, 2014, Vol. 57, No. 4, pp. 167–176. © Allerton Press, Inc., 2014. Original Russian Text © V.V. Zelenskiy, S.V. Nesterenko, L.P. Bannikov, 2014, published in Koks i Khimiya, 2014, No. 4, pp. 43–52.

CHEMISTRY

Corrosion Resistance of Nickel Steel and Nickel Alloys in Aggressive Media V. V. Zelenskiya, S. V. Nesterenkob, and L. P. Bannikovc a

PAO Zaporozhkoks, Zaporozhe, Ukraine Kharkov National Urban University, Kharkov, Ukraine email: [email protected] c Ukrainian CoalChemistry Institute, Kharkov, Ukraine email: [email protected]

b

Received February 7, 2014

Abstract—The corrosion resistance of austenitic steel and nickel alloys is studied in the most aggressive media within the chemical shops of coke plants: in the stock solutions of the sulfate department and in sulfu ricacid solutions used for the purification of crude benzene. In the study, the most dangerous ions, activating corrosion in 10X17H13M2T steel, are CNS– ions, which are capable of destroying the passive layers on chro mium–nickel–molybdenum steel in the stock solutions of the sulfate department. Research shows that sul furicacid solutions used for the purification of crude benzene are very aggressive in relation to highalloy steel, titanium, zirconium, and copper. Possible structural materials for use in contact with such solutions include the nickel alloys ХН63МБ, ХН65МВНУ, and Hastelloy C276. Keywords: coke plant, sulfuricacid exposure, austenitic steel, corrosion resistance, weld seams, microalloy ing, rareearth metals, pitting, free corrosion potential DOI: 10.3103/S1068364X14040097

Sulfuric acid is a very corrosive to metals. Its use as an absorber or catalyst leads to the formation of media that are more aggressive than the pure acid with respect to regular and highalloy steel. Such media include the stock solutions of the sulfate department and solutions used for the purification of crude benzene. At present, in the coke industry, it is very important to protect weld joints in the sulfate department from corrosion, especially on account of the introduction of saturatorfree systems that contain dozens of welded valves, hundreds of meters of welded largediameter pipe, and many welded components made from acid resistant steel. The stock solution in the sulfate depart ment contains sulfuric acid, ammonium sulfate, chlo rides, H2S, and HCN. The composition of the stock solution with 3–10% acidity is as follows, according to [1]: 400–450 g/dm2 sulfate ions; 0.2–2.8 g/dm2 chlo rides; 0.065–0.160 g/dm2 cyanides; 0.1–1.2 g/dm2 thiocyanates; 0.002–0.050 g/dm2 total iron (Fe2+, Fe3+); and 10–20 g/dm2 pyridine bases. The presence of pyridine bases somewhat moder ates the aggressive action of the stock solutions used in the sulfate department. However, at a concentration of 10–20 g/dm3, their protective action in 6–10% sulfu ric acid at 60°C is no more than 50–60% [2]. The con tent of mineral salts and H2S in cokeoven gas, with practically no O2, hinders the formation of protective passive films on the surface of chromonickel steel,

according to the data in [3]. Hence, local corrosion (such as pitting corrosion) occurs. In addition, corro sion is stimulated by increasing the temperature and speed of the solutions. Purification of the benzene–thiophene fraction of crude benzene is based on treatment by concentrated sulfuric acid (93.0–94.5%) in the presence of unsatur ated compounds (the piperidine fraction), with subse quent neutralization of the product by alkali solution (12–15%), as illustrated in Fig. 1. Continuousaction equipment is used here. In the interaction of the ben zene–thiophene fraction with concentrated sulfuric acid and additives, several parallel reactions occur, including the following: ⎯alkylation of thiophene; ⎯polymerization of unsaturated compounds in the additives and fractions; ⎯sulfurization of the phenolic hydrocarbons and alkylation products. The pyridine bases present in the crude benzene are removed; they form pyridine sulfate on reaction with the sulfuric acid. In the subsequent neutralization of the purified fraction, phenols are removed in the form of sodium phenolates. Purification occurs mainly in the pumps and hydraulic mixers (ball and tangential mixers). In such equipment, effective mixing only occurs at the system’s upper limits of productivity.

167

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ZELENSKIY et al. Carbon disulfide fraction

Crude benzene

Points where samples are taken for corrosion tests

C1

NaOH (2%) 5

Additive Acid 4

Benzene–thiophene fraction

2 3

1 Spent acid from the second stage

Fig. 1. System for the purification of crude benzene: (C1) rectification column; (1, 4) groups of hydraulic ball mixers; (3) group of static mixers; (2, 5) contact equipment.

For more effective mixing of the reagents and puri fied fraction, static mixers have been developed and introduced in the chemical shop at PAO Zaporozh koks. The mixers take the form of a pipe with soldered plates positioned so that the reagent flux passing through the mixer changes direction at least ten times. That ensures turbulent flow of the liquid phase with little hydraulic drag. Such mixers replace some of the ball mixers and all of the tangential mixtures in the two lines for sulfuric acid purification. Industrial tests show that, when using static mixers, the flow rate of acid and additives is reduced (relative to comparable traditional systems) when the thiophene content in the benzene has been sufficiently reduced. This indicates more effective mixing of the reagents with the fraction to be purified. Note, however, that the reliability of the static mixer depends on the materials from which it has been made. The medium used in purification is extremely corrosive. Low and highalloy steel cannot be used in the manufacture of such systems. In the present work, we consider the corrosion resistance of austenitic steel and alloys in stock solu tions of the sulfate department and in sulfuricacid solutions used for the purification of crude benzene and develop methods for boosting the corrosion resis tance on the basis of alloying with rareearth metals and the use of new highmolybdenum steel and nickel alloys. Gravimetric tests for different coke plants indicate intense and nonuniform corrosion of carbon and chromium steel in the stock solutions of the sulfate department (Table 1). Chromonickel austenitic steel of type 18–10 and economically alloyed steel are sus

ceptible to local corrosion and so are unsuitable for use in the sulfate department. We find that 10X17H13M2T, 10X17H13M3T, and SMO254 austenitic steel and 06XH28MДT alloy are relatively resistant to corrosion. These materials are used in saturators and saturatorfree systems. The resistance of highalloy steel largely depends on the aggressiveness of the stock solution, which, in turn, depends on the impurities present. The influence of the stock solution’s composition is assessed by the capacitive–ohmic and potentiostatic methods. These methods provide information regard ing the adsorption of the corrosive particles on the sur face of the metal, which significantly affect the elec trochemical solution of the steel. We investigate stock solution from the sulfate department at PAO Zaporozhkoks (saturator process) and also stock solution from the saturatorfree pro cess. The composition of the solution from PAO Zaporozhkoks is as follows: ⎯sulfuric acid 6 wt %; ⎯ammonium sulfate 408 g/dm2; ⎯chlorides 1.5 g/dm2; ⎯thiocyanates 0.2 g/dm2; ⎯pyridine bases 18 g/dm2. The composition of the solution from the satura torfree process is as follows: ⎯sulfuric acid 12 wt %; ⎯ammonium sulfate 380 g/dm2; ⎯chlorides 2.5 g/dm2; ⎯thiocyanates 1.3 g/dm2; ⎯pyridine bases 12 g/dm2. COKE AND CHEMISTRY

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Table 1. Gravimetric corrosion tests of steel and alloy samples in the sulfate departments of coke plants Corrosion rate, g/(m2 h) test location

Material circulation pan of saturator

evaporator of saturatorfree stageII circulation collector system

0.72–4.9 0.16–0.33* 0.06–0.093* 0.01–0.05 0.004–0.03 0.06–0.92* 0.91–0.98* 0.78–1.07* 0.001–0.02 0.005–0.006

Cт3 08X18H10T 10X17H13M2T 10X17H13M3T 08X17H15M3T 08X22H6M2T 08X22H6T 08X17T 06XH28MDT alloy SMO254

5.24–6.15 0.58–6.15* 0.08–0.20 0.05–0.12 0.02–0.03 0.4–1.98*

6.20–6.80 0.35–1.44* 0.07–0.15 0.06–0.09 0.07–0.08 1.35–1.4* Not determined Not determined

0.01–0.02 0.02–0.04

0.004–0.06 0. 003–0.06

* Local corrosion.

If we analyze the electrical capacitance, resistance, and solution currents for the metal–solution bound ary as a function of the polarizing potential, we find that the maximum anodiccurrent density corre sponds to the maximum differential capacitance and minimum resistance. That permits wide use of the capacitive–ohmic characteristics of phase boundaries to assess the corrosion of metal in electrolyte solutions (Fig. 2) [4]. A frequencydependent maximum of the capaci tance is observed in the range from 0.1 to –0.06 V and is associated with Faraday solution of the steel. The height of the maximum in the solution current depends on the molybdenum content of the steel. Highalloy 10X17H13M3T steel is more resistant to such media and is characterized by minimum capaci tance in the active and passive states. The corrosion resistance of steel with no molybdenum is consider

C, µF cm–2 300

ably less. SMO254 steel is promising, since it con tains 6% molybdenum and has considerable corrosion resistance in the stock solutions. It follows from Fig. 2 that, with cathode polariza tion, the corrosion resistance is a function of the molybdenum content in the electrodes: with higher molybdenum content, the resistance of the phase boundary is greater, the solution currents are smaller, and hence the corrosion resistance is greater. With active solution, the resistance of the phase boundary is considerably reduced (by practically an order of mag nitude). The decrease in logR is greatest for 12X18H10T chromonickel steel. The introduction of corrosion activators in model solutions increases their corrosive activity and hence the change in parameters of the double electric layer. The adsorption of the corrosive particles at the metal

logR [Ohm cm2] (b) 2.5

(a)

j, mА cm–2

(c)

2.0 2.0

1

200

1.5

2

1.0

1.5

1

2

3

100

1.0

3

1

2

0.5 3

0.5 0.2

0.1

0

–0.1 E, V

0.3

0.2

0.1

0

–0.1 –0.2 E, V

0.3

0.2

0.1

0

–0.1 E, V

Fig. 2. Dependence of the capacitance (a), resistance R (b), and current density j (c) on the potential ΔE for the phase boundaries in the stock solution of the sulfate department at 60°C: (1) 12X18H10T steel; (2) 10X17H13M2T steel; (3) 10X17H13M3T steel. COKE AND CHEMISTRY

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ZELENSKIY et al. C, µF/cm2 150

4 3 100

2 1

50 0.2

0.1

–0.1

0

–0.2 E, V

Fig. 3. Dependence of the capacitance at the phase boundary between 10X17H13M2T steel and model solutions on their com position, at 60°C: (1) 12% H2SO4; (2) 12% H2SO4 + 420 g/dm3 (NH4)2SO4 + 5 g/dm3 NaCl; (3) 12% H2SO4 + 420 g/dm3 (NH4)2SO4 + 10 g/dm3 NaCl; (4) 12% H2SO4 + 420 g/dm3 (NH4)2SO4 + 10 g/dm3 NaCl, with the injection of cokeoven gas.

C, µF/cm2

1500

1000

3 1

500

2 0.1

0

–0.1

–0.2

–0.3 E, V

Fig. 4. Influence of the CNS–ion concentration on the capacitance at the phase boundary between 10X17H13M2T steel and the model solution containing 12% H2SO4 + 420 g/dm2 (NH4)2SO4, when its concentration in solution is 0.5 (1), 1.0 (2), and 2 (3) g/dm2.

surface greatly changes the capacitive characteristics of the phase boundary (Figs. 3 and 4). The introduction of chloride ions (5–10 g/dm3) increases the capacitance of the double electric layer (Fig. 3). However, increase in the chloride content has about half the influence on the capacitance at the boundary between 10X17H13M2T steel and the stock solution, which increases by only 10–15%. This is associated with the presence of a large quantity of sul

fate ions in the solution: 420 g/dm3 (NH4)2SO4 [5]. The hydrogen sulfide in cokeoven gas (2.2 g/m3) also changes the parameters of the double electric layer. However, its activating effect in FeHS+ form is consid erably less than that of thiocyanates [6, 7]. The intro duction of CNS– in the model solution sharply increases the capacitance of the double electric layer and shifts the freecorrosion potential to negative val ues. The maximum of the pseudocapacitance COKE AND CHEMISTRY

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Fig. 5. Corrosion of a gaspipeline weld seam in a 10X17H13M2T steel saturator.

07X19H11M3 steel weld seam

10X17H13M2T steel

Fig. 6. Corrosion of a gaspipeline weld seam in a 10X17H13M2T steel saturator (×400).

(a)

increases in proportion to the thiocyanate content in solution until it exceeds the baseline level with no added CNS– by factors of 10–12 (Fig. 4). Metallographic analysis of sections of 12X18H10T and 10X17H13M2T steel shows distinctly nonuniform solution. That indicates different stability of the phase structures in steel with different content of the alloying elements. According to our findings, chromium–nickel– molybdenum steel containing at least 3% molybde num is the most resistant to sulfuricacid media. By contrast, chromonickel steel cannot be used as a struc tural material in the sulfate department. Tests of sam ples in solutions from the sulfate departments of dif ferent coke plants confirm these conclusions (Table 1). Study of the adsorption properties of different impurities indicates that the most dangerous activators of corrosive processes at 10X17H13M2T steel are CNS– ions, which are able to break down the passive layers on chromium–nickel–molybdenum steel in the stock solutions of the sulfate department. The life of weld joints in stainlesssteel saturators is between 5– 6 months and three years (depending on the steel and the electrodes). Failure is due to corrosion of the fused layer (Fig. 5) and the basic metal along the line of the seam (Fig. 6). Welded 10X17H13M2T and 10X17H13M3T steel pipes fail after 1.5 years of operation in saturatorfree systems on account of disintegration of the fused metal (Fig. 7). The life of weld seams in 10X17H13M2T steel produced by НЖ13 and ЭA400/10у electrodes is 2– 4 years, depending on the aggressiveness of the medium; that is insufficient [7]. Analysis of laboratory data shows that, by microal loying the fused metal with 0.0250–0.0032% yttrium, the corrosion resistance of the weld seam may be increased by a factor of 3–4. Accordingly, we have developed an electrode coating that contains yttrium– silicon alloy (with 25% yttrium). An experimental batch of ЛК1 electrodes of this type manufactured at Frunze Sumy ScientificProduction Facility has (b)

Fig. 7. Corrosion of a transverse pipe seam (a) and an annular flange seam (b) in a pipeline of a saturatorfree system. COKE AND CHEMISTRY

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ZELENSKIY et al. 3 log j [A/cm2]

E, V (standard hydrogen electrode)

–100

0

1 1'

0

2

2'

2 1 0

+100 1 +200

+800 1

0

2 log j [A/m2]

1

Fig. 8. Potentiodynamic curves for 10X17H13M2T steel and weld seams produced by ЛK1 and НЖ13 electrodes in the stock solutions of the sulfate department at 60°C: (0) 10X17H13M2T steel; (1) basic metal of the second weld seam produced by ЛK1 electrodes; (1') metal of the first weld seam produced by ЛK1 electrodes; (2) metal of the second weld seam produced by НЖ13 electrodes; (2') metal of the first weld seam produced by НЖ13 elec trodes.

undergone industrial tests at PAO Zaporozhkoks and several other coke plants. The corrosion resistance of weld seams produced using the experimental and massproduced electrodes was investigated in plant and laboratory conditions. The experiments included the following components: ⎯determination of the corrosion resistance of massproduced and experimental weld seams by elec trochemical measurements and industrial tests; ⎯industrial and operational tests of the welded equipment. Table 2. Electrochemical heterogeneity of 10X17H13M2T steel weld seams, mV Electrodes Steel Basic metal Thermalinflu ence zone Weld seam

3

4

5

Fig. 9. Solution current of weld seams with different degrees of alloying at the Flade potential in the stock solution: (1) 12X20H10Б steel (ЦЛ11 electrodes); (2) 12X23H13Б steel (ЦЛ9 electrodes); (3) 03X19H14M2.5 steel (ОЗЛ20 electrodes); (4) 07X19H14M3 steel (НЖ13 electrodes); (5) 07X19H14M3 steel + rareearth metal (ЛK1 electrodes).

+300

2

2

ЛK1

НЖ13

ЦЛ11 ОЗЛ17у

–38 –42

–39 –42

–40 –65

–35 –20

–45

–58

–128

+10

Analysis of the polarization curves for the weld seams and unwelded sections of 10X17H13M2T steel in the stock solutions of the sulfate department at 60°C shows that the corrosion resistance of the weld seam is mainly determined by the resistance of the seam and the thermalinfluence zone. As follows from the polar ization curves, the weld seams of 10X17H13M2T steel after double heating are characterized by higher solu tion currents in the active and passive regions (Fig. 8, curves 2 and 2'). For microalloyed steel (Fig. 8, curves 1 and 1'), the difference in corrosion resistance of the weld seams (first and second seams) is considerably less than for the unalloyed steel. The anodic behavior of the weld seams may be associated with structural transforma tions in the metal after double heating and with the considerably greater stability of the seam containing rareearth metal. In Fig. 9, we show potentiostatic data for the corro sion resistance of 10X17H13M2T steel weld seams with different degrees of alloying, produced by means of ЦЛ9, ЦЛ11, НЖ13, НИАТ1, ЭА400/10у, ОЗЛ20, and ЛК1 electrodes in the stock solutions of the sulfate department at PAO Zaporozhkoks. The corrosion of the weld seam and the type of fail ure depend on the surface distribution of the electrode potential. The electrode potential is measured at weld seams (thickness 12 mm) of 10X17H13M2T steel pro duced by massproduced and experimental electrodes (ЦЛ9, ОЗЛ17у, НЖ13, and ЛК1). Table 2 pre sents measurement data for the electrode potential of weld seams produced by those electrodes in 5% H2SO4 solution with the addition of 0.1% NH4CNS. In investigating the heterogeneity of the potential distribution perpendicular to the seam (Table 2), we find that the heterogeneity is much reduced by microalloying with rareearth metal. In other words, the potential difference between the weld seam and the COKE AND CHEMISTRY

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Table 3. Mechanical properties of weld seam Steel 10X20H9Г6T After microalloying with yttrium 12X18H10T After microalloying with yttrium 07X19H11MЗ After microalloying with yttrium

σB, MPa

σy, MPa

δ, %

ψ, %

Ac, J/cm2

590 610 595 600 560 580

340 340 340 350 360 380

42 45 25 36 40 44

57 60 32 44 58 58

190 220 99 130 190 220

basic metal is reduced (from 25–32 mV to 5–6 mV), whereas the potential of the thermalinfluence zone is practically unchanged (–42 mV). For comparison, we study the heterogeneity of weld seams produced by means of ЦЛ11 electrodes, which are known to be poorly corrosionresistant in such media. In that case, the difference between the weld seam and the basic metal is increased to 88 mV, while the potential of the thermalinfluence zone falls to –65 mV. The use of ОЗЛ17у electrodes manufactured on the basis of 03XH28MДT steel wire sharply increases the corrosion resistance of the weld seam. In that case, the basic metal is the anode, while the more alloyed seam is the cathode. Thus, in terms of effectiveness, microalloying of the weld seam with rareearth metal is largely equivalent to increasing the content of chro mium, nickel, and molybdenum in the seam. Microalloying with rareearth metal affects the mechanical properties of the weld seams. Analysis of the results in Table 3 indicates that the structural changes in the weld seam due to microalloying improve its mechanical characteristics. The strength, plasticity, and ductility are enhanced.

Table 4. Corrosiontest data for 10X17H13M2T and 12X18H10T steel weld seams in the sulfate department (1250h tests) Content of rareearth metal, wt % Electrode

НЖ13 ЦЛ11 ЛK1

in electrode coating

in weld seam

– – 1.0Y

– – 0.0028Y

Corrosion rate, g/m2 h 0.1030* 0.2832* 0.0025

* Local failure of metal.

Corrosion tests of 10X17H13M2T and 12X18H10T steel weld seams in the sulfate depart ment at PAO Zaporozhkoks (Table 4) show that 10X17H13M2T steel weld seams produced by means of electrodes with rareearth metal are highly corro sionresistant in industrial conditions; that is consis tent with the results of laboratory electrochemical and corrosion tests. The samples after tests in the sulfate department are shown in Fig. 10.

(a)

(b)

(c)

(d)

Fig. 10. Samples of 10X17H13M2T steel weld seams produced by means of НЖ13 (a), ЭА400/10у (b), ОЗЛ17u (c), and ЛK1 (d) electrodes after tests in the sulfate department. COKE AND CHEMISTRY

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Table 5. Corrosion resistance of metals and alloys in the reagent used in crudebenzene purification Material

Content of alloying elements, %

Corrosion rate K, mm/g

Type of corrosion

06XH28MДT alloys

Cr 22–24; Ni 26–28; Mo 2.5–3.0; Cu 2.5–3.5

3.56

Uniform

03XH28MДT alloy Titanium Zirconium

As above Ti Zr

3.36 7.53 8.42

As above Pitting As above

XH30MДБШ (ЭK77Ш) alloy

Cr 27; Ni 30; Mo 3.5; Cu 1.5

0.84

Uniform

H70MФВВИ alloy

Ni 73; Mo 26

0.0008

As above

XH65MБ alloy XH65MБУ alloy XH63MБ (ЭП758Б) alloy C276 Hastelloy

Cr 15; Ni 65; Mo 16 As above Cr 20; Ni 63; Mo 16 Cr 17; Ni 65; Mo 16

0.013 0.009 0.012 0.011

As above As above As above As above

In the tests, the 12X18H10T steel weld seams have poor corrosion resistance. However, introducing rare earth metal improves the corrosion resistance and somewhat slows the corrosion of the weld seams [9]. Metallographic analysis of weld seams obtained by means of electrodes alloyed with rareearth metal shows considerably less local corrosion (pitting and

point corrosion). These electrodes were used to weld the 10X17H13M2T steel saturator, pipe, and stores employed in the reconstruction of the sulfate depart ment at PAO Zaporozhkoks and other coke plants. Regular inspections of the equipment indicate high corrosion resistance of the weld seams produced with the experimental LK1 electrodes. Such electrodes are recommended in welding corrosionresistant austen ite steel for use in the sulfate departments of coke plants. Table 5 presents the results of 250h tests in sulfu ricacid wash fluid, when 90 kg of the concentrated (95%) H2SO4 is added to 1 t of the benzene– thiophene fraction. The alloy samples are introduced as inserts in fluoroplastic pipe, by means of fluoroplas tic cassettes (Fig. 11) [10]. Analysis of the test results shows that the best mate rials for use in such conditions are XH63MБ, XH65MВУ, and Hastelloy C276 nickel alloys. Tests of an experimental mixer made of Hastelloy C276 nickel alloy in the chemical shop (the benzene washing department) at PAO Zaporozhkoks indicate good performance and reliability. CONCLUSIONS

Fig. 11. Cassettes for the insertion of metal samples in pipelines carrying aggressive reagent used in the purifica tion of crude benzene.

(1) Experiments have shown the factors responsible for the corrosiveness of the fluid used in the sulfate department of coke plants. COKE AND CHEMISTRY

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Fig. 12. Chemical shop at PAO Zaporozhkoks.

(2) On the basis of the adsorption of different anions in the stock solutions of the sulfate department at the surface of austenitic steel, we may conclude that the most dangerous ions, activating corrosion at 10X17H13M2T steel, are CNS– ions, which are capa ble of destroying the passive layers formed on chro mium–nickel–molybdenum steel. (3) Industrial gravimetric tests show that chrome steel has no corrosion resistance in the stock solutions of the sulfate department, while 12X18H10T chromon ickel steel has little resistance. The corrosion resis tance is best for 10X17H13M2, 10X17H13M3T, 10X17H15M3T, and SMO254 steel, as well as 08XH28MДT alloy. (4) Gravimetric and electrochemical tests show that weld seams microalloyed with rareearth metal exhibit considerably greater (by a factor of 3–4) corrosion resistance to corrosive cokeplant media than do weld seams produced by means of НЖ13 and ЭA400/10у electrodes. Electrochemical data show that 07X19H11M3 steel weld seams microalloyed with rareearth metal are more resistant to pitting corro sion. (The solution currents are reduced at a pitting potential E = 0.18 V.) COKE AND CHEMISTRY

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(5) Industrial gravimetric tests show that the sulfu ricacid solutions used for the purification of crude ben zene are very aggressive in relation to numerous struc tural materials. Highalloy steel and metals such as tita nium, zirconium, and copper cannot be used for such equipment. Also inapplicable are 06XH28MДT, 03XH28MДT, and XH30MДБ alloys, with poor corro sion resistance in the sulfuricacid solutions used for the purification of crude benzene. (6) Possible structural materials for use in contact with such solutions include the nickel alloys XH63MБ, XH65MВУ, and Hastelloy C276. Tests of an experimental mixer made of Hastelloy C276 nickel alloy in the chemical shop at PAO Zaporozh koks indicate good performance and reliability. REFERENCES 1. Kolyandr, L.Ya., Ulavlivanie i pererabotka khimicheskikh produktov koksovaniya (Capture and Processing of Coking Products), Moscow: Metallurgizdat, 1962. 2. Altsybeeva, A.I. and Levin, O.Z., Ingibitory korrozii: spravochnik (Corrosion Inhibitors: A Handbook), Len ingrad: Khimiya, 1968.

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6. Iofa, Z.A. and Fang, L.K., Acceleration of the dis charge reaction of hydrogen ions at iron by hydrogen sulfide, Zashch. Met., 1974, vol. 10, no. 1, pp. 17–21.

solutions, Zashch. Met., 1970, vol. 6, no. 4, pp. 491– 493. 8. Nesterenko, S.V. and Khanin, A.M., Corrosion protec tion of equipment in the sulfate department, Koks Khim., 1988, no. 5, pp. 48–51. 9. Nesterenko, S.V., Efimenko, I.G., and Balan, L.N., Corrosion resistance of microalloyed weld seams in flu ids used in cokeplant chemical shops, Koks Khim., 1992, no. 8, pp. 32–35. 10. Rubchevskii, V.N., Chernyshov, Yu.A., Zelenskii, V.V., et al., Corrosion resistance of nickel alloys as structural materials used in systems for the sulfuricacid process ing of crude benzene, Uglekhim. Zh., 2013, no. 3, pp. 41–47.

7. Iofa, Z.A., Action of hydrogen sulfide on the corrosion of iron and on the adsorption of inhibitors in acidic

Translated by Bernard Gilbert

3. Khanin, A.M., Berdnikova, R.D., Melikentsov, B.I., and Sidorenko, I.S., Behavior of weld joints in acidic sulfate solutions, Koks Khim., 1980, no. 7, pp. 55–58. 4. Nesterenko, S.V. and Dzhelali, V.V., Electrochemical behavior of highalloy steels in acidic sulfate solutions, Vestn. Khar’kovsk. Politekhn. Inst., 1989, no. 265, pp. 81–83. 5. Rozenfel’d, I.L. and Maksimchuk, V.P., Passivating properties of anions, Zh. Fiz. Khim., 1961, vol. 35, no. 11, pp. 2561–2567.

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