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Studying the Efficiency of Inhibitors in Chemical Cleaning of Heat-and-Power Equipment by Citric Acid Solutions

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Abstract

The results of laboratory studies concerning corrosion inhibitors that make it possible to decelerate the metal dissolution in heat-and-power equipment during its chemical cleaning are presented. The features of the decrease in the carbon steel corrosion rate using commonly known corrosion inhibitors, such as urotropin, captax, and thiourea, as well as an imported reagent based on alkylbenzene dimethylammonium chloride (hereinafter referred to as IK), are considered. An effect of the process temperature and the concentration of inhibitors exerted on their protective properties and the kinetics of metal corrosion is analyzed. In the first part of the paper, it is shown—based on the gravimetric method for corrosion testing—that the efficiency of captax, captax with neonol AF 9-12, thiourea (0.05 wt %), and reagent IK (0.2 wt %) at a temperature of 70–80°С for the protection of carbon steel from corrosion in a 5% solution of ammonium monocyrate amounts to 60–77%, which is higher than that with the use of urotropin. The high efficiency of inhibitors in the deceleration of steel corrosion in the 5% solution of ammonium monocyrate is caused by a strong inhibition of both electrode reactions of the metal. The results of corrosion tests using a polarization resistance technique are presented. Two parts of a decrease in the steel corrosion rate are clearly distinguished on the curves of an instantaneous corrosion rate. The decrease is caused by the formation of a protective film with the participation of an inhibitor and a subsequent stabilization of this film. The results of corrosion tests in the solutions of ammonium monocyrate with added inhibitors, such as captax, captax + AF 9-12, and reagent IK, that confirm the low instantaneous corrosion rate of carbon steel are discussed. These compositions could be used for chemical cleaning of heat-and-power equipment as well as for increasing its efficiency and reducing repair costs.

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Author information

Correspondence to R. T. Burganov.

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Translated by O. Polyakov

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Burganov, R.T., Gilmullina, A.R., Kirilova, M.A. et al. Studying the Efficiency of Inhibitors in Chemical Cleaning of Heat-and-Power Equipment by Citric Acid Solutions. Therm. Eng. 67, 68–71 (2020). https://doi.org/10.1134/S0040601520010012

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Keywords:

  • chemical washing
  • acid corrosion
  • corrosion inhibitor
  • protective efficiency
  • corrosion rate
  • captax
  • citric acid