Non-Destructive Electrochemical Testing for Stainless-Steel Components with Complex Geometry Using Innovative Gel Electrolytes

Abstract

Corrosion can be a problem for stainless steels in chloride-containing or other aggressive environments, especially when they are formed as components with complex shapes. Monitoring the corrosion performance of the stainless steels during their in-service life is not always an easy task. Traditional electrochemical cells can be difficult to adapt to complex surfaces, and undesired crevices or liquid electrolyte leaks can occur. In the presented work, the possible use of non-destructive techniques with innovative gel electrolytes was investigated using portable cells. The electrolytes were based on agar (used as a gelling agent with ionic conductivity), glycerol (a plasticizer that improves adaptability to complex surfaces), and NaCl or KClO 4 salts (which improve the conductivity and control the aggression of the tests). X-ray photoelectron spectroscopy (XPS) and Mott-Schottky analysis were carried out to obtain information about the influence of the electrolyte on the passive layer. The oxygen concentration and conductivity in the gels with various glycerol contents were compared to those in liquid electrolytes. Electrochemical impedance spectroscopy (EIS) measurements were carried out in liquids and gels. The performance of the gel cell on a stainless-steel component with a weld and complex shape was checked. The variation in the sensitivity of gels with and without chlorides to identify corrosion-susceptible regions was tested.

Agar versus Agarose Gelled Electrolyte for In Situ Corrosion Studies on Metallic Cultural Heritage

“…This indicates that agarose slightly increases the measured corrosion rate, although this effect is much less relevant than for agar . Diffusion does not seem to be affected by the use of the gel in the case of bronze, in agreement with a previous work, but for weathering steel the diffusive impedance is increased, what might be explained by the lower oxygen content of gelled electrolytes . In any case, as it has been shown in the results of previous section (Figures –), the uncertainties of field measurements are higher than these effects.…”

“…Agar is a translucent, cheap, non‐toxic, and quick and easy to prepare material, which admits a wide range of aqueous electrolytes and also contributes to conductivity. It's flexibility allows adaptation to irregular surfaces and can be improved by the addition of plasticizers,, and its syneresis helps wetting the surface and allowing good contact. Other proposed materials, have shown other limitations: Commercial or synthetized anionic gels are very limited by the electrolyte choice, and the use of PVA has to be more deeply studied, as preliminary results showed appreciable differences when compared to a traditional cell design.…”

Electrochemical noise measurements on stainless steel using a gelled electrolyte

“…More information about the gel manufacturing process can be found in a previous publication [16]. The conductivity of the gel electrolyte at room temperature was 3.5 mS cm -1 , its pH 6.6, its oxygen content 2.9 ppm, and its viscosity around 2 Pa s [16,17]. A liquid electrolyte consisting of a 0.5 wt % liquid solution of NaCl was used to compare the EN signals generated by the corrosion processes.…”

“…The usefulness of this innovative electrolyte has already been tested for studying corrosion of stainless steel (SS) surfaces with complex geometry using d.c. polarization techniques [16] and EIS measurements [17]. The present paper presents a pioneering study on the use of the EN technique in ZRA, galvanostatic, and potentiostatic modes for investigating electrochemical processes in an electrochemical cell with gel electrolyte.…”

An Improvement of Quality of the Rear Cover of Bearing Turbine with the use of Selected Methods

“…The way of identifying the nonconformities on the product without violating its surface is to make the research with non-destructive tests, which except that allow to identify the nonconformities without violating the surface of the product, also they meet the need of the steel industry and they do not change the usable properties of the tested products. After the overview of the newest publications (from period of year 2019 -2017) about the non-destructive tests, it was concluded that the non-destructive tests were made in order to analyze of products (Corbett and Tronca, 2017;Velay-Lizancos et al, 2018, Hong et al, 2018 in these the products from metal (Peterka et al, 2018;Markus et al, 2018;Monrrabal et al,2018;Trung and Pham, 2017;Zhang et al, 2017) or composite products (Komarkova et al, 2018;Swiderski, 2019). It was researched the depending of parameters or measure the mechanical properties and theses influence on the quality of test or products (Trung and Pham, 2017;Beskopylny et al, 2017;Sorger et al, 2019;Aghadavoudi-Jolfaei et al, 2018).…”