Aggressive Conditions Influence on the Rust Structure in the Chemical Production of the South Kazakhstan

Abzalova D. A., Rizaeva D. S., Abramova G.I. 

International Kazakh-Turkish University named after H.A. Yassavi

Shymkent Institute

Metal and metal items corrosion fighting still remains the most serious problem in the national economy, actually, solving this problem will provide for the effective usage of the main funds almost in every field, which consume the metal constructions.

Constructions and equipments in the non-ferrous metallurgy are operating under the influence of different aggressive conditions: acid gases (HCl, SO2, SO3, Cl), high air moisture content – more than 75 %, mineral acids solutions of various concentration and so on. In these conditions carbon steel corrosion velocity is more than 0,5 – 1,0 mm/per year, anti-corrosion  plating lose their protective characteristics before the fixed period, corrosion is revealed under the plating film, and this provides for the plating destruction.

Rust composition and characteristics in different operating conditions are often not taken into account while fulfilling anticorrosion services, particularly while choosing the type of surface preparation. Metal corrosion products, formed in the different operating conditions possess different phase and chemical composition (1-3, 6).

So, investigation of equipment rust composition performed in the Stock Company ‘Shymkentmai’ and hydro metal and sulphuric acid workshops equipment performed in the Stock Company ‘Yuszhpolymetal’ presented some interest.

Roentgen –structural analysis of the corrosion products performed in  different surfaces of the equipment and constructions of the above mentioned workshops proved that corrosion products having colours from light brown to dark brown with different shadings contain in their composition mainly, magnetite, hematite, vustite, and mixed ferric oxides. Corrosion products enhance partially porous structure, and in some places – tight coalescence  layer.

The main ferric oxidizing product in the air corrosion of the carbon steels is FeOOH hydroxide, which undergoes crystallization in several modifications. Rust phase composition is almost always represented by α –FeOOH (hetite)  and γ – FeOOH (lepidochronite). These substances proved to be good sorbents.

Hetite and lepidochronite in the rust are mixed with the magnetite              (Fe3 O4), while the latter may be in the form of the thinnest interlayer. In these conditions the magnetite Fe3 O4   takes little moisture and is not prone to swelling. Different performance of these three products in the changing air conditions is mainly determined after the rust process.

There are general tendencies and differences in the process of the aggressive gases absorption by the hetite and lepidochronite. The quality of the absorbed sulphuric gas is increasing when the air comparative moisture content is increasing, this may be stated as the general tendency. SO2    content increasing in the air leads to the increasing of its absorption.  The link character of the air moisture with sulphate concentration testifies to the fact of the SO2   dissolution in the absorbed water, besides absorption.  Acid solution easily penetrates through the rust layer to the metal and enhances corrosion.

However, lepidochronite is the more active absorber than hetite at every gas concentration in the air. It is well known from scientific sources that lepidochronite is more easily dissolved in the acids and salt acid solution than hetite, that’s why the acid formed at dissolving is much more wasted in the chemical reactions mainly with lepidochronite.

It has been stated that aggressive condition corrosion products of the Stock Company ‘Yuszhpolymetal’ enterprises contain up to 20% of sulphates and up to 5 % of chlorides.

 O2   - content in the air is of great importance for the corrosion.  The authors - researchers have supposed that SO2   should act as an oxidizer like oxygen.

However, it is possible that corrosion was caused by sulphuric acid influence, which is formed in the reaction of SO2, O2 and H2 O; whereas it is catalyzed by the ferric oxide. As a result, Fe SO4 appears in the rust in the form of the hygroscopic impurity, water solution of which has acid reaction as the result of hydrolyze. Consequently, as the result of such oxidation, ferric sulphate catalyzes rusting, entering the further reactions. According to the experimental data magnetite is of particular importance in the oxygen reduction mechanism (Stock Company ‘Yuszhpolymetal’ sulphuric acid workshop). Ferric oxide as an ordinary rust contacting the metal ferric and the solution of the ferric sulphate is easily reduced to the magnetite, which in its turn is easily oxidized by oxygen. Consequently, Fe3 SO4     magnetite thin layer is in the surface of ferric, the pores of which are easily filled with Fe SO4 solution of (7-9).

The ferric is dissolved in the form of the Fe+2 ions in this solution, the ions in their turn partially oxidized to Fe+3, and solid phase of Fe3 O4 is formed. A thick layer of Fe OOH or Fe2 O3 is placed over the magnetite.

Cathode conjugate reaction of the corrosion process consists of electrons transition through the semi conducting magnetite to the contact points between Fe3 O4 and Fe OOH particles, where the electrons reduce  Fe OOH to Fe3 O4.

This reaction mechanism is important because of the formation of such elements; during this process a spacious division of corresponding local electrodes may take place. As a result of this Fe SO4 acidic solution high local concentrations appear, just as in the pitting corrosion. Actually, this may be an explanation of the aggressive conditions influence on rust structure.

 

Reference:

 

1. Enterprise Anticorrosion Service. Reference book. - Stepanov I.A., Savelyeva I.Ya., Figovsky O.A. – M.: Metallurgy, 1987. – 240 p.

2. Anti-corros. Meth. and Mater., 1982, V.29, N. 8, P.18.

3. Bagazhkov S.G., Sukhanova N.A. Laboratory Manual in Liquor-Paint Plating Technology. – M.: Chemistry, 1982. – 240 p.

4. Belov A.V., Slavutskaya A.M. // Digest: Experimental Methods study of the corrosion processes in the aggressive conditions of the chemical production. – M.: NIITECHim, 1985. – P. 129-130.

5.Voitovich V.A. Compounds for painting corrosion surfaces of the ferrous metals (rust modifiers). Survey of the foreign research literature. Serial Fighting Corrosion in the Oil and Gas Industry. – M.: VNIIOENG, 1974.

6.Voitovich V.A. Usage of Special Plating to Protect Constructions from Corrosion and Processing of the Surfaces. Research – technical survey. Serial ‘Corrosion and Corrosion Fighting in the Oil and Gas Industry. – M.:  VNIIOENG, 1974.

7. Kluzhin D.V., Babayan Ye., Abzalova D.A. Rational Usage of the Natural Resources in the South Kazakhstan // Proceedings of the research-practical conference ‘Chemistry and Chemical Technology in the 21th  Century’. – Tomsk (Russia), 2005.

8. Kluzhin D.V., Nakipbekova G., Abzalova D.A. Study of the Protecting Properties of the LPPK, Based on the Microbiology Industry Wastes // Proceedings of the research-practical conference ‘Chemistry and Chemical Technology in the 21th  Century’. – Tomsk (Russia), 2005.

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Technological Characteristics of SKU-8TB Based on the Xylitane Polyether

Abzalova D.A., Rizaeva D. S., Abramova G.I.

International Kazakh-Turkish University named after H.A. Yassavi

 Shymkent Institute  

         Technological properties of rubber produced by different vulcanization systems (hydrogen peroxide, dimension hydrogen peroxide) were tested to characterize SKU-8TB raw rubber; its resistance to the aggressive conditions was also studied (laboratory samples).

The following properties were used to characterize raw rubber samples SKU-8TB based on the xylitane polyether:

1.     solubility in the ethyl acetate (State Norms 8981-93)

2.     glass casting temperature  (State Norms 12254-86)

3.     viscosity according to Muni (State Norms 10722-94)

SKU-8TB different raw rubber samples technological properties were studied. The main part of the raw rubber samples were completely dissolved in the ethyl acetate, this testifies to the fact that it is of linear structure and there are no cross links.  Some dissoluble polymer samples were obtained, and this may be explained by the fact that the ratio of some starting components has been changed. SKU-8TB raw rubber glass casting temperature is in the limits of -40/-430 C. Comparing SKU-8TB with SKU-8PG, glass casting temperature of which is in the limits -34, 5/-35,50C, we may say, that raw rubber SKU-8TB has much more low Ts values.

         The deviations stated are explained by the fact that poly ethers with larger molecular mass were used for the synthesis of these raw rubbers. Ratio viscosity according to Muni was used for the technological evaluation of the raw rubber. It should be noted, that this ratio is in the broad limits depending on the synthesis temperature and correlation of the starting components. We may state that poly urethane SKU-8TB (viscosity limits from 20 to 150 conditional units) is easily processed in the cold rolls (1-2).

         Determination of the processing period influence on the SKU-8TB technological characteristics was fulfilled by measuring viscosity value according to Muni at different rolling periods.

         Pelt  for determining viscosity according to Muni was manufactured in the laboratory rolls of 160 x 320 mm size, friction was 1: 24/ 1, 27; the front roll rotation velocity was 23 – 27,5 revolutions per minute, the gap between the rolls was 1,0 – 0, 05 mm.

         Raw rubber was processed in the rolls, where the rolls’ temperature was 250 C; the processing period varied from 5 to 20 minutes.

         Variations of SKU-8TB viscosity according to Muni depending on the processing period at 250 C were investigated.

         The curve testifies that if the processing period is increased, viscosity according to Muni is lowered; it may be connected with the partial destruction of the polymer. It was also necessary to clarify the possibility of the SKU-8TB raw rubber processing by casting under pressure, because this method turns to be the most productive. This method is possible for using if the viscosity according to Muni ratio is higher than 70 conditional units (3-4).

         To achieve this xylitane poly ether P-6 BA (the amount is 1,5 and 10 mass parts) was added to the sample of SKU-8TB raw rubber with the starting viscosity according to Muni, equal to 113 conditional units. Data of P-6 BA additives influence on the viscosity according to Muni is given in the table 1.

 

 

 

 

 

Table 1.

Influence of xylitane poly ether P-6 BA on the technological properties of SKU-8TB raw rubber

Quantity of P-6 BA, introduced into the raw rubber, mass part

Viscosity according to Muni, conditional units

0

131

1, 0

94, 5

5, 0

76, 7

10, 0

70, 7

 

         As it is clear from the table, introduction of 5-10 mass parts of the plasticizer leads to the lowering of the viscosity according to Muni from 131 to 70 conditional units it enables us to use this method with different values of viscosity according to Muni.

         Physical – mechanical indexes of the vulcanizors, filled with the xylitane poly ether up to 10 mass part., meet the requirements of the State Norms for the raw rubber SKU-8TB.

Reference:

1.     Apukhtina N.P. Raw Rubbers of Special Assignment / Digest. Editored   by I.V. Garmonov. – M.: VINITI.-P. 85.

2.     Zuyev Yu. Strength and Destruction of Elastic Materials. – M.: Chemistry, 1994.

3.     Korotkina D.Sh., Livshits K.S. and others. Synthesis and Properties of Non-Crystallized Urethane Raw Rubber. –M.: VNIISK, 1970. –  P. 45.

4.     Kusakov V.G. Oil Products Physical and Chemical Characteristics Methods of Analysis. – M., 1966.