The corrosion behaviour of type 316L stainless steel in aqueous 30–50 wt%. NaOH at temperatures up to 90 °C has been elucidated. Exposure to room temperature environment showed parabolic weight loss behaviour, with corrosion rates of up to 0.4 mm/year. Higher NaOH concentrations and exposure temperatures resulted in a reduced stability of the electrochemical passivity domain, associated with higher corrosion rates. Exposure to de-aerated 50 wt%. NaOH presented corrosion rates of up to 0.5 mm/year at open circuit potential, with maximum corrosion rates under polarisation of up to ≈ 18 mm/year. The formation of a dark iron-oxy-hydroxide and nickel-oxide was observed, with exposure to temperatures in excess of 50 °C. The behaviour of type 316L stainless steel in hot caustic environment is compared to types 204, 304, 2205 stainless steel, and nickel alloy 200.Graphic

The corrosion product formation and the stress corrosion cracking of brass in different ammonia environments have been observed and characterized. Optical and scanning electron microscopy techniques were used to analyze the corrosion phenomena on the systems. The testing methodology was designed to investigate the variables affecting stress corrosion cracking behaviour, these parameters were: stamp geometry, immersion time, Cl^- concentration, pH, copper ions concentration, exposure to vapour/ liquid. From this investigation, stress corrosion cracking of brass was shown to occur most severely in ammonia vapour. The increase of the amount of ammonia and copper ions in the form of copper sulphate was found to increase the corrosion of the brass samples.

Most knowledge of polar corrosion comes from atmospheric exposure trials; in situ immersion data for Antarctic infrastructure are nearly absent, and immersion in glacier meltwater has, to our knowledge, not been previously reported. During the XXIX Ecuadorian Antarctic Expedition, ASTM A36 carbon steel coupons were immersed for up to three weeks at Pedro Vicente Maldonado Station (Greenwich Island) in two chemically contrasting waters, namely coastal seawater (34.3 PSU, 48.5 mS cm⁻¹) and glacier meltwater (0.04 PSU, 79.3 µS cm⁻¹; conductivities measured at 18–20 °C), which have an approximately 600-fold conductivity difference. Corrosion rates were determined gravimetrically (ASTM G1/G31) and cross-checked with open-circuit potential, linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP). Gravimetric rates showed no statistically significant difference between environments (47 ± 4 µm yr⁻¹ in seawater versus 51 ± 9 µm yr⁻¹ in glacier meltwater; Welch’s t-test, p = 0.28), directly contradicting the expectation that higher conductivity and chloride content would accelerate attack. Raw LPR suggested an apparent five- to ten-fold higher polarization resistance in glacier meltwater, but EIS showed that this was almost entirely uncompensated solution resistance (median Ru·A ≈ 14 kΩ cm²), whereas the EIS-derived polarization resistance was of the same order in both waters (median Rp·A ≈ 2.4 kΩ cm² in seawater and 1.3 kΩ cm² in glacier meltwater). PDP consequently underestimated the glacier corrosion rate (≈7 µm yr⁻¹) due to IR-drop distortion of the Tafel slopes in the low-conductivity electrolyte. Scanning electron microscopy and energy-dispersive X-ray spectroscopy showed Fe- and O-rich corrosion products in both waters, but seawater forms a dense, continuous, and chloride- and sodium-bearing crust, while glacier meltwater forms sparse, isolated florets incorporating silicon from glacial rock flour and no detectable chlorine. The results show that, over a single Antarctic summer, glacier meltwater is not a benign environment for carbon steel and that gravimetric measurement, rather than uncorrected electrochemical techniques, is required to obtain reliable corrosion rates in low-conductivity polar waters.

This work describes an efficient and environmentally friendly method for the synthesis of silver-based nanostructures through a green route using Aloe vera extract as a reducing agent, silver nitrate (AgNO₃) as a precursor, and polyvinylpyrrolidone (PVP, 10 kDa molecular weight) as a stabilizing agent. The formation of these structures was supported by UV–Vis spectroscopy, where a surface plasmon resonance (SPR) band was observed between 425 and 460 nm. Scanning electron microscopy revealed predominantly spherical features in the 300–500 nm range; however, the distinction between primary nanoparticles and aggregates cannot be conclusively established from SEM alone. EDX analysis indicated a silver content of 59.96 wt%. Antibacterial assays performed in Z8 medium demonstrated a reduction in cyanobacterial growth with increasing dosage, with complete inhibition observed at ≥20 $\mu$L (nominal MIC = 1.77 mg mL⁻¹, based on precursor estimation). Total dissolved solids and absorbance measurements exhibited a decreasing trend with increasing concentration (effect size = 0.87, $p<0.001$), supporting an inhibitory effect under the tested conditions. These findings suggest potential antibacterial activity. However, this study should be considered exploratory, and further work is required to elucidate the underlying mechanisms.