The article presents the results of a study, of the effect of basalt fiber materials on the corros1on resistance of pipe metals. The samples of basalt fibers were studied as a reason of corrosion. The tests were made according to ASTM G189 "Standard guide for laboratory simulat1on of corrosion under insulation". During the work, an experimental laboratory facility was designed to determine the corrosion rate under materials. To research the effect of the chemical composition of the samples on the corrosion process under fiber materials the influence of the leaching of chemically active anions after wetting and heating of basalt fiber were investigated. Based on the obtained results, the main factors contributing to the development of corrosion under insulation were determined, and recommendations for reduction were given. It was found that samples with open porosity showed a tower corrosion rate. The reported study was funded by RFBR according to the research project № 18-29-17068.

Atmospheric corrosion is a serious problem given destruction of various materials, especially metals. Chloride deposition is one of the most significant factors for this. This factor is important not only in marine localities but also in localities where the de-icing salts may deposit on structures´ surfaces. The paper shows results of long-term measurement of chloride deposition rates and comparison of standardised methods. The distribution model from road sources is presented in the map.

Mild steel is widely used in fabrication of reaction vessels, storage tanks, petroleum refineries, and so on, but it is severely attacked in acid solutions. Despite continuing advances in development of corrosion-resistant materials, the use of chemical inhibitors often remains the most practical and cost-effective means of preventing corrosion. Organic compounds containing nitrogen, sulphur, oxygen, and heterocyclic compounds with a polar functional group and a conjugated double bond have been reported to inhibit mild steel corrosion. There are a wide range of organic inhibitors but unfortunately most of them are expensive and health hazardous. Thus, it remains an important goal to find low cost and eco-friendly inhibitors. Few non-toxic compounds belonging to pharmaceutically active compound group have been investigated for their corrosion inhibition properties for mild steel in acid media. Plant extracts are rich sources of environmentally acceptable corrosion inhibitors. The plant extracts non- toxic and readily available. These extracts contain many organic compounds which have polar atoms such as O, N, P and S. They are adsorbed onto the metal surface through these polar atoms; protective films are formed. Adsorptions of these ingredients obey various adsorption isotherms for example Langmuir adsorption isotherm and Temkin isotherm. In present work we have reviewed structural feature of few green corrosion inhibitors and their mechanism of corrosion inhibition by analysing data from weight loss measurements, tafel polarization and EIS investigations.

S235JR steel is used in many applications, but its resistance to the erosion processes has been poorly studied. To investigate this resistance, cavitation and slurry erosion tests were conducted. These tests were carries out at different erosion intensities, i.e. different flow rates in the cavitation tunnel with a system of barricades and different rotational speeds in the slurry pot. The steel was tested as-received and after thermal treatment at 930^oC, which lowered the steel hardness. To better understand the degradation processes, in addition to mass loss measurements, surface roughness and hardness were measured. Along with increasing erosion intensity, the mass loss increased as well. However, the nature of the increase in mass loss, as well as the effect of steel hardness on this mass loss, was different for each of the erosion processes. In the cavitation erosion tests, the mass loss increased linearly with the increase in flow velocity, while in the slurry tests this relationship was polynomial, indicating a strong increase in mass losses with increasing impact velocity. Cavitation erosion resulted in stronger and deeper strain hardening than slurry. Surface damage from cavitation erosion tests was mainly deep pits, voids and cracks while during the slurry tests, flaking was the most significant damage.

Polymeric blends of Hydroxypropyl cellulose (HPC) and Polyurethane (PU) (PU/HPC_20/80; PU/HPC_50/50; PU/HPC_80/20) have been prepared by solvent (DMF) casting method and investigated after exposure to accelerated ageing conditions by using a mercury lamp (200 < λ< 700 nm), at 60% humidity and 40 ^oC for 600 h. Their hydrolytic stability was evaluated after immersing them for 48 h in different pH (2.6 and 7.4) Phosphate-Buffered Saline (PBS) media. The structural changes in the composition of blends during the accelerated weathering and hydrolysis processes have been investigated by means of FT-IR (Fourier Transform Infrared) spectroscopy and DSC (Differential Scanning Calorimetry) analysis. FT-IR spectra of the blends after 600 h of irradiation and 48 h hydrolysis in PBS solutions revealed a major degradation process especially in the HPC component and in the soft segment of PU. The changes in the crystallinity of the blends have been also evaluated by FT-IR (by determination of Total Crystallinity Index (TCI) and Lateral Order Index (LOI)) and DSC that evidenced the reduction of the melting enthalpy ((DH_m) and of its corresponding crystallization (Tc) on heating/cooling runs indicated that ageing strongly affects the crystallinity of the PU/HPC blends.

Abstract: The replacement of environmentally harmful chromate coatings has been of great interest to the electrochemical industry. Compact silica coatings are a widely discussed inorganic coating alternative, to replace previously used toxic materials. Silica offers a feasible and simple method of passive corrosion protection, with the option of enhancement by incorporating different inhibitors into the matrix. Tannic acid is a non-toxic substance, that acts as cathodic corrosion inhibitor, by forming metal-tannate protective barriers. [1,2] The present study discusses the addition of different concentrations of tannic acid in nano-scale silica coatings, which were prepared by sol-gel technique and dip-coating method on Zn substrates. Long term corrosion measurements were carried out on the prepared substrates to check their durability and corrosion resistance. The thin layers were characterized by Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarization Curves. It has been concluded that silica coatings containing tannic acid show promising EIS values and corrosion current densities, compared to the simple silica coatings.

References:

[1] E.Kushimerek, E. Chrzescijanska, Mater. Corros., 2015, 66(2), 169-174.

[2] B. Qian, B. Han, M. Zheng, Corros. Sci., 2013, 72, 1-9.

Post-tensioned (PT) construction incorporating bonded tendons with cementitious grouts has been used for highway bridges. The tendon duct and the encapsulating grout materials provide barrier corrosion protection for the embedded high-strength steel strand. Although generally used in good engineering practice, cases of PT tendon corrosion have been documented relating to inadequate detailing for joints, development of grout bleed water, and more recently in the past several years- segregation of thixotropic grouts. In the latter case, cases of thixotropic grouts (that have been developed to mitigate grout bleeding) developed physically and chemically deficient grout that has been characterized to have high moisture content and elevated sulfate ion concentrations. The early presence of elevated sulfate ion concentrations in the deficient grout was attributed to hinder stable steel passivation. Case studies of PT corrosion associated with grouts with elevated sulfate concentrations are presented followed by a review of electrochemical techniques and measurements used to identify the role of sulfates in steel corrosion in alkaline solutions such as polarization techniques, electrochemical impedance spectroscopy, and electrochemical noise.

Colophony microcapsules synthesized by water in oil in water double emulsion containing NaNO₂ corrosion inhibitors were investigated for controlled release in simulated concrete pore solutions. With high encapsulation efficiency of 83% measured by induced coupled plasma optical emission spectroscopy, the microcapsules were introduced to solutions of deionized water (pH 6.8), carbonate bicarbonate buffer solution (pH 9.1), and simulated concrete pore solution made of saturated calcium hydroxide (pH 12.6) to measure the corrosion inhibitor release. Due to the pKa of colophony, the corrosion inhibitors experienced a faster release in alkaline solutions of pH 9.1 and 12.6. Additionally, the corrosion inhibitive performance was determined by electrochemical impedance spectroscopy and potentiodynamic polarization to protect carbon steel rebars from chloride induced corrosion and carbonation.

Electroless nickel-boron (ENB) coatings from borohydride-reduced bath have received wide acceptance thanks to their excellent hardness and superior wear resistance. Therefore, they have been considered as an alternative to hard chrome. However, the presence of a small amount of toxic heavy metals such as Pb or Tl in the plating bath restricts their application. These metallic salts are used to stabilize the bath, which is necessary to avoid abrupt decomposition and is harmful to the environment. A new bath, that is exempt from stabilizer, was designed for ENB plating. In this bath, the bath stability is achieved through the optimization of the concentration of complexing agent, pH adjuster, and reducing agent. An ENB coating from the new bath presents promising properties including modified surface morphology, excellent hardness, low friction coefficient, etc. Salt spray test (ASTM B117-07) and potentiodynamic polarization test results showed that the new ENB coating has a significantly better corrosion resistance than the conventional ENB coatings stabilized by Pb or Tl salts.

In conclusion, the present ENB coating is produced in an environmentally-friendly bath, and the deposit presents properties close to those of the conventional ENB deposit.

Corrosion of iron in acidic medium similar to the acid rain water (pH=3.6) at various rotation speeds was investigated. Investigation included inhibiting effect of two new green formulations containing oils extracted from the seeds of Jatropha curcas (labeled JAC) and Aleurite moluccana (labeled ALM). The inhibition efficiency was evaluated by electrochemical measurements, after performing the automatic ohmic drop compensation (ZIR). The results obtained shows that the increase of the rotation speed, leads an increase of the current density (from 75.57µA/cm² at 0 rpm to 99.09 µA/cm² at 1500 rpm). This increase can be explained by the increase in the amount of dissolved oxygen at the electrode surface in the acidic rain solution (pH=3.6). Also, the two environment-friendly corrosion inhibitors act as mixed type inhibitors that protected iron against the corrosion in the acidic solution. The inhibition efficiency increases with an increase of the inhibitor concentration to attain a maximum of 97% and 96% at 250 ppm of the ALM and the JAC respectively .