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Juvenis scientia 2019 № 11-12 | Биологические науки
УДК: 57.036 ГРНТИ: 34.31.21 DOI: 10.32415/jscientia.2019.11-12.01
THE USE OF FRUIT FRESH JUICES AS INHIBITORS OF ALUMINIUM ELECTROCHEMICAL CORROSION IN ALKALINE MEDIUM
A. A. Sikachina ©
Immanuel Kant Baltic Federal University 2 University St., 239000 Kaliningrad, Russia
H Sikachina Andrey - sikachina@list.ru
In this article, the anticorrosion properties of inhibitors (that is, fruit and berry processing products) are studied using an electrochemical cell with irreversible electrodes as an example, in which cathode surface (aluminum sample for testing the class "AD1 pl") is highly renewable. A sample of crudely processed copper (needed to minimize polarization at hydrogen evolution) of the "M00 k" class serves as an anode. A measure for corrosion is a change in the amperage of a galvanic electrochemical cell.
Keywords: aluminum, copper, fruit fresh juice, corrosion inhibitor, galvanic electrochemical cell, adsorption, hydrogen depolarization.
ИСПОЛЬЗОВАНИЕ ПРОДУКТОВ ПЕРЕРАБОТКИ ПЛОДОВО-ЯГОДНОГО СЫРЬЯ ПРИ КОРРОЗИИ В ЩЕЛОЧНОЙ СРЕДЕ
А. А.Сикачина
Балтийский Федеральный Университет имени Иммануила Канта Россия, 239000 г. Калининград, ул. Университетская, 2
ЕЗ Сикачина Андрей Анатольевич - sikachina@list.ru
В публикуемой статье антикоррозионные свойства ингибиторов (продуктов переработки плодово-ягодного сырья) исследуются на примере электрохимического элемента с необратимыми электродами, катодная поверхность (образец алюминия для испытаний класса «ЛД1 пл») которого высоко возобновляема. Образец грубо обработанной меди (необходимый для минимизации поляризации при выделении водорода) класса «M00 к» служит анодом. Коррозия оценивается по изменению силы тока гальванического электрохимического элемента.
Ключевые слова: алюминий, медь, ингибитор коррозии, гальванический электрохимический элемент, адсорбция, деполяризация водорода.
Electrochemical corrosion of aluminum both in Russian Federation and abroad was studied mainly in the acidic environment of inorganic acids [2, pp. 6; 8, pp. 2234], and, in a smaller number of scientific papers, in salt [3, pp. 209] environment. In an alkaline environment, aluminum has a much more electronegative standard potential (-2.35 V) compared to acidic solutions (-1.66 V). The activating ability reaches maximum values at pH 15 ... 16, and the corrosion rate is 150 ... 170 g/m2 x hour, i.e. is the highest of those listed in [2, pp. 8; 3, pp. 212; 8, pp. 2237]. In foreign studies, water or alcoholic extracts of plants of various types are used: vegetables [7, pp. 452], fruit and oil [2, pp. 11], ferns [9, pp. 320], and also waste from food production [6, pp. 1137].
In the early years of the 21st century, mainly in Russian publications and in Arabian publications, chemicals of a synthetic nature of diverse classes were used as individual corrosion inhibitors [1, pp. 288; 5, pp. 530]. But in connection with the tightening environmental policies of the European Union and the United States, their application in real practice is difficult. According to the available literature, not many studies have been done regarding the corrosion behavior of 6063 aluminum alloy in phosphoric acid medium as well as with sodium hydroxide medium. Even though dissolution rate of aluminium in H3PO4 medium is lower, compared to the dissolution of the same substance in hydrochloric medium or sulphuric acid medium, it does corrode aluminium and its alloys [8, pp. 2244].
The novelty of this scientific article is the study of electrochemical corrosion in an alkaline medium, since it has
not been studied enough [4, pp. 6; 8, pp. 2241]. The study is conducted in the presence of inhibitors (inh) of processed fruits and vegetables (in this scientific article called "fruit fresh juice"), which corresponds to the latest environmental standards of European Union and USA. The partial influence of the inhibitor-mixture components is also investigated using the Pearson's correlation coefficient for statistical analysis.
Research methods. Selection of a corrosion system.
For description of the experiment refer to figure 1.
Figure 1. Electrochemical galvanic cell. Blue arrows indicate the parameters of secondary or other galvanic cells
Organic inhibitors of the corrosion process. What are the inhibitors and how are these inhibitors obtained.
Juices (100%) were used as potential corrosion inhibitors. These juices were obtained from fresh products using ordinary mechanical extraction and filtration through a cotton filter and used immediately. No other actions that could distort the physicochemical composition were performed.
As inhibitors, the juices were placed into the electrolyte in amount of 10 mL (they become 8.3% when placed in the electrolyte of the electrochemical galvanic cell).
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luvenis scientia 2019 № 11-12
The estimated chemical composition of the tested "fruit fresh juice" was taken from the website http://www.intelmeal. ru.
To calculate the Pearson's correlation coefficients for individual nutrients of fruit and berry juices, those classes of organic substances were selected that make up the chemical composition, the amount of which is more than 0.01 g (not counting the ash content and the amount of water, which also revealed the I-m - correlation relationship).
It was tested as a corrosion inhibitor 0.07 N NaBr (this concentration is acquired when a weighted charge is placed in the electrolyte of electrochemical cell) to show more clearly the difference between an organic inhibitor and an inorganic inhibitor.
The technology of experiment.
Amperage.
Amperage of the galvanic cell on figure 1 was measured every minute (stopwatch) with PECAHTA1 YX-360 Trn multimeter (Russian Federation).
At the time of immersion of the aluminum sample in a corrosive medium and at the time of initial reading, the time in minutes was accepted as zero, and the milliammeter readings were much higher than all others, since the instantaneous galvanic cell are on figure 1 too.
With a high concentration of alkali with action in interfering element (written briefly) —Al\H2O\Cu+ or —Al\ H2O, inh\Cu+ can be neglected. The time of the experiment with each inhibitory additive was different. The criterion for end of experience cycle was the equality of amperage values for 3 minutes.
Hydrogen depolarization.
To analyze the polarization phenomenon at the anode, the
author chose the volume of depolarized hydrogen (H2O+e-->
Hads+OH-), which was measured using 0.01 mL microburette. Organic inhibitors acted on the overpotential of hydrogen evolution on copper, being chemically-adsorbed on copper. The H2-gas level was measured according to any minute called n was recorded when 0.02 mL of H2-gas was released.
Pearson's correlation coefficients.
The Pearson's correlation coefficients values were compiled with MS Excel 2010; they reflected the relation between the amperage value and chemical composition in "fruit fresh juice" (i.e. — I-m). The amperage was applied for n = 1 ... 3.
Results and interpretations experiment. Amperage in the both corrosion process A and process B, mA.
Amperage in the both corrosion process A and process B is presented in figure 2. — without inhibitor is implied as a reference.
Table 1
Mathematical supplement: equations of the curves line in Figure 2
An inhibitor: presence or absence Line equation in Figure 2
Without inhibitor y = 0.069x2 - 1.562x + 11.68
Malus domestica y = 0.098x2 - 1.451x + 7.998
Viburbum opulus y = 0.055x2 - 0.960x + 5.807
Citrus reticulata y = 0.023x2 - 0.528x + 4.660
Vitis vinifera y = 0.058x2 - 0.858x + 4.444
Solanum lycopersicum y = 0.024x2 - 0.407x + 3.388
0.07 N NaBr y = 0.090x2 - 1.902x + 18.60
The best inhibitors are those that prevent for run of electron density from water-molecules on anode surface and reduce the recombination of H .-atoms with that in 2H ^
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H2 reaction. All inhibitors reduce the amperage values, since the inhibiting composition is hydrated by H2O-molecules, on the graph it looks like the decrease in amperage as a function of time. Moreover, the decrease in amperage in the presence of both citrus "fruit fresh juice" and solanum "fruit fresh juice" is the smoothest.
Further, it is the chemical composition of "fruit fresh juice" that determines the best inhibitor. It is — vitis "fruit fresh juice". The worst inhibitor is — malus "fruit fresh juice".
The contribution of chemical composition in the amperage Recognized by applying Pearson's correlation coefficients (Table 2)
Table 2
The contribution of the main multiple components in "fruit fresh juice" for amperage value decreasing
Mass m of organic compounds in inhibitor Amperage I at number of minutes n
1 2 3
"I-m" - correlation coefficients
Carbohydrates +0.81 +0.65 +0.62
Of which both monoses and disaccharides +0.31 -0.02 -0.09
Of which sucrose -0.03 +0.13 +0.31
Of which glucose +0.11 -0.27 -0.41
Of which fructose +0.39 +0.04 -0.06
Of which dietary-fiber -0.10 -0.35 -0.63
Fats +0.47 +0.43 +0.22
Proteins -0.67 -0.67 -0.54
Water -0.90 -0.75 -0.67
Ash-content +0.59 +0.49 +0.49
5
il
< 9 E
_- 7
0 1 2 I 4 5 6 7 B 9 10 11 1Z Time, minute
Wfchout irihibtur Malus domestica VitE vinifera
Solarium tycopersicunn Citrus reticulata Viburnum opulus
NsBr, 0.:7 N
Figure 2. Amperage in both electrochemical cell A and B in dependence of time, minute
1 RESANTA (In English language)
The author uses an unusual and strange at first glance correlation of I-m.nternal H2O and amperage, since the degree of dilution of organic substances within a specific "fruit fresh juice" can affect the manifestation of the anticorrosive properties of organic substances within a specific "fruit fresh juice". More water inside a particular juice - less reduction in amperage.
The greatest value of +I-m - correlations is on the first minute of experiments, then its value is decreasing. This is caused by smaller polarization of the anode (by lower electron density). The increase in the correlation coefficients over time is achieved in sucrose, which is a non-reducing disaccharide and does not carry a negative center in its structure.
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Juvenis scientia 2019 № 11-12 | Buo^orMHecKue HayKU
The hydrogen depolarization in copper-anode.
Comparison takes place on the example of the best inhibitor and worst inhibitor.
Table 3
The gas-separation due to depolarization of Cu-anode
Аn inhibitor: presence or absence The minute on which the volume of H2 is 0.02 mL Total volume of H2, mL /-value at zero minute2
Without inhibitor < 1 0.27 20.0
Citrus reticulata 3 0.19 13.0
Solanum lycopersicum 4 0.04 13.0
Viburnum opulus 5 0.05 11.5
Vítis vinífera 5 0.08 10.0
Malus domestica 6 0.06 9.0
0.07 N NaBr 6 0.20 18.0
H2 - gas emissions are higher in vitis "fruit fresh juice". This is due to a greater change in the properties of the electrolyte. There is a competition between the speeds of the following processes H2O+e— ^ Hads+OH— (1) and 2Hads ^ H2 (2). In the presence of vitis "fruit fresh juice" the process (1) proceeds more slowly than the process (2). In the presence of malus "fruit fresh juice" the process (1) proceeds faster than the
2 Due to the oscillation of the galvanometer needle due to the rapid dissolution of the oxide film, the values are rounded
REFERENCES
process (2). This is due to colloidal processes (adhesion, a certain charge on the surface of copper, etc.), because inhibitor juices were simply squeezed from the fruit pulp and were not subjected to any other physicochemical processes.
A high amperage with 0.07 N NaBr (which is also a reducing agent: Br2+2e— ^ 2Br—, and the electrochemical potential is +1.06 V) is explained by the dissociation of NaBr, i.e. by an increase in the ionic concentration for 2 times. This means that there is an inversely proportional dependence on the ionic strength, which organic components of juices do not create.
Conclusion.
By its nature, the surface of aluminum has a high negative charge, which can be judged by comparing the zero potential of aluminum and its stationary corrosion potential. According to the given scale of Antropov's potentials, the surface aluminum is negatively charged. Aluminum is one of the non-transition metals that are characterized by weak adsorption activity.
Therefore, 8.3% solutions of fruit juices (which they become when an electrochemical cell is placed in an electrolyte), on average, halve the amperage developed by a galvanic cell (for example, the worst inhibitor) and 1.5 times the volume of depolarized hydrogen. From analysis of correlation coefficients, it was found that the manifestation of inhibiting properties is influenced by percent of carbohydrates, and the percentage of sucrose has the most decisive influence. These data characterize fruit and berry juice as inhibitors of medium strength and allow us to recommend them for more in-depth studies and implementation, although the high cost of such products in Russian Federation could limit their practical use.
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Received 02.12.2019
