Francesca Guidi

Tryptamine as a green iron corrosion inhibitor in 0.5 M deaerated sulphuric acid

The inhibition effects of tryptamine (TA) on the corrosion behaviour of ARMCO iron in 0.5 M deaerated H2SO4 (in the 25–55 °C temperature range) was studied in both short and long time tests (1, 24 and 72 h) by means of potentiodynamic curves (PCM) and electrochemical impedance spectroscopy (EIS). TA was found to be an effective ARMCO iron inhibitor, even at 55 °C and 72 h, but only at 10 mM. At this concentration the inhibition percentages (IP%), calculated by PCM and EIS, ranged from 90% to 99% and did not diminish over time and as the temperature increased. TA adsorption followed Bockris–Swinkels’ isotherm (x=1). The thermodynamic data indicated that, in the more concentrated solutions, TA also chemisorbed on the iron surface.

Tryptophan as copper corrosion inhibitor in 0.5 M aerated sulfuric acid

The use of Tryptophan (Trp) as a copper corrosion inhibitor was tested in 0.5 M aerated sulfuric acid (H2SO4) in the 20–50°C temperature range. Its effectiveness was assessed through potentiodynamic (at 1 h, 72 h, 6 months), spectrophotometric (72 h tests) and gravimetric (72 h tests) tests. At 20–50°C (1 h tests) the Trp adsorption followed Bockris–Swinkels isotherm (x=2). The Trp even underwent over time (six month) a photodegradation, but surprisingly enough this did not affect the inhibition percentage (IP) which was 80% for the solutions kept in the dark as well as those kept in light.

Heavy metal pollution studies by resuspension experiments in Venice Lagoon

Abstract A mechanical device for sediment resuspension has been used in Venice Lagoon for sampling extremely thin surface sediment layers, allowing the characterization of the top few tenths or hundredths of a millimetre. The age of the resuspended layer was estimated at two sampling stations from the sedimentation rate to be about 2 weeks. Zinc and iron were determined (nitric acid extraction) in particles of the resuspended layers and in the corresponding underlying sediments. Lower metal concentrations were detected in sediments (43–323 μg/g for Zn and 9200–17400 μg/g for Fe) with respect to resuspended particles (63–424 μg/g for Zn and 12,200–25,400 μg/g for Fe). The remarkable concentration decreases of zinc (both in resuspended particles and in sediments) from the inner areas of the lagoon (Porto Marghera) seaward, can be attributed to the decreasing effects of industrial pollution. The relatively high concentrations of iron observed in areas far from Porto Marghera, can be explained by the contribution of runoff waters or by contamination from nearby polluted sediments. Higher metal concentrations in resuspended particles were observed in April than in February (1987). Concentration increases for zinc (from 7 to 91%) were more substantial than for iron (from not significant to 42%). Zinc uptake by plankton, followed by deposition of residual organic materials onto the sediment surface is suggested as an explanation of the higher metal concentrations detected in April. These results reflect the particular features of the proposed technique, which, at least for cohesive and fine grained sediments, seems to be promising for future applications in studies both on the tracing of metal pollution sources and on the migration processes of these contaminants between sediment and overlying water.

Corrosion protection and mechanical performance of SiO2 films deposited via PECVD on OT59 brass

Purpose – To evaluate the corrosion performance and nano‐mechanical behaviour of a brass substrate covered by different thick SiO2 layers deposited by means of plasma enhanced chemical vapour deposition (PECVD) technique.Design/methodology/approach – The comparison between laboratory and “industrial” objects revealed a very good corrosion behaviour and good mechanical performance of both of them: in particular it was possible to modulate the surface treatment to solve various problems from the industrial point of view.Findings – It was possible to reduce the Cu migration into the SiO2 coating during the PECVD deposition at a negligible level and to control it by the deposition; further, the nano‐indentation tests revealed the great utility of the coating annealing in obtaining a significant improvement of the mechanical properties of the coated objects.Research limitations/implications – Even if some industrial problems were solved (minimization of the presence of the coating defects and transparency of t...

Acid–base equilibria of co-ordinated ligands. Part 1. The effect of basicity of co-ordinated nitrogen donors upon the acidity of chelating 8-aminoquinoline in some dicationic platinum(II) complexes

Cationic complexes of the type [Pt(8NH2-quin)L2][ClO4]2, and [Pt(8NH2-quin)(L–L)][ClO4]2(8NH2-quin = 8-aminoquinoline), where L and L–L are mono- and bi-dentate nitrogen donors respectively, have been prepared. In aqueous solution, they undergo reversible deprotonation of the amino group of the quinoline ligand. The corresponding ionization constants (Kac) have been determined by UV/VIS spectrophotometry at 25 °C and I= 0.1 mol dm–3. The linear free-energy relationship pKac=α+βpKaL is verified for the para-substituted phyridines, pKaL referring to the basicity of L in water at 25 °C.