Corrosion is a critical industrial problem. To solve this problem, the present research analyzed the influence of corrosive media on the efficiency of a guayusa inhibitor. Therefore, guayusa extract was obtained, and five groups of ASTMS A36 steel test tubes were prepared, each with variable extract concentrations (200 ppm, 400 ppm, 600 ppm, 800 ppm, and 1000 ppm) that were exposed to different corrosive media (5% NaCl, 5% NaCl + acetic acid, 1% HNO₃, and 10% HNO₃). The results obtained were compared to determine the percentage efficiency of the inhibitor in each of the corrosive media. This study provides a detailed understanding of how the corrosive environment influences the effectiveness of a guayusa inhibitor, which is used as a green inhibitor for the first time, allowing its viability and performance to be assessed under various conditions.

The fabrication of miniaturized and durable pH electrodes is a key requirement for developing advanced analytical devices for both industrial and biomedical applications. Glass electrodes are not an option in these cases. Electrodes based on metal oxides have been the most studied for pH sensing in these and other applications. Stainless steel pH electrodes have been an option for many years, both for measurement using steel as a sensitive material and using it as a substrate for the deposition of other metal oxides; in the latter case, the sensitive ability of stainless steel seems to play a crucial role. In addition, recent use as a substrate for materials such as polymers, carbon nanotubes, and metallic nanoparticles should be considered. This paper presents a review of this type of pH electrode, covering aspects related to the sensing mechanism, the treatment of stainless steel, potentiometric performances, applications, and the prospects of these sensors for use in modern analytical instruments. Sensing with the oxide passive layer and the artificial layer by oxidation treatments is analyzed. The use of metal oxides and other materials as the sensitive layer on stainless steel, their application in wearable devices, microneedle sensors, and combination with field-effect transistors for high-temperature pH sensing are covered as the most current and promising applications.