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In the present work, the protective properties of inhibitive pigments in two epoxy‐primers against corrosion of the aluminium alloy 2024T3 in marine atmosphere were investigated, the first containing SrCrO₄ and the second Zn₃(PO₄)₂. Potentiostatic polarisation and impedance measurement methods were utilised to evaluate, both the spontaneous onset of defects on coated samples and the propagation of a small artificial defect of known dimension applied since the beginning of the test on each sample, during 24 months of exposure to the marine atmosphere. These techniques enabled a quantitative evaluation of the protective efficiency of the two primers to be made, and for the effects of the surface pre‐treatments of the metallic substrate to be investigated.

The salt‐spray test is still today often utilized to control the anticorrosive performance of paints applied on metallic substrates. The time required for this test method is much shorter than that necessary to carry out the atmospheric exposure test (some weeks instead of many years). Nevertheless the results provided by the salt spray test are only qualitative and their extrapolability to the real behaviour of the paint system's film‐metallic substrate is very difficult. Moreover, in some cases there is a discrepancy between the results of the salt spray test and the reality; for instance, it was observed some time ago that hot‐dip galvanized steel constitutes a better substrate for paints than bare steel, whereas the salt spray test results indicate the contrary. The present work represents only a part of a more conspicuous set of observations devoted to a comparison of laboratory and field results. In this first stage we examined, by means of salt spray and total immersion tests, the behaviour of bare steel and hot‐dip galvanized steel substrates, both phosphatized and coated by the same paint. The aim of this work was to ascertain if the results of the two methods are in accordance and, moreover, to compare the qualitative information given by the salt spray tests with those, quantitative, obtained by the electrode impedance technique on specimens immersed in 3% NaCl solution. By means of this technique it is possible to determine at the same time the values of the paint film resistance, of its capacitance, of the polarisation resistance and of the double layer pseudocapacitance related to the corrosion taking place on the metallic substrate and to ascertain the eventual intervention of diffusive phenomena into the corrosive process. Finally, this electrochemical method, because its non‐destructive nature, permits one to observe the variation of the values of overmentioned parameters as a function of time and therefore to interpret the evolution of the corrosion process.

This article has been withdrawn as it was published elsewhere and accidentally duplicated. The original article can be seen here: 10.1108/eb007296. When citing the article, please cite: C. Wrubl, A. Mollica, U. Montini, A. Litigio, (1991), “Corrosion performance of cataphoretically painted specimens: A comparison between salt spray and continuous immersion tests”, Anti-Corrosion Methods and Materials, Vol. 38 Iss: 6, pp. 11 - 15.

There is an increasing demand for eco‐friendly inhibitors for use in cooling water systems. Both calcium gluconates and molybdate are eco‐friendly, non‐toxic chemicals. The corrosion inhibition of calcium gluconate and sodium molybdate on carbon steel in neutral aqueous media was evaluated by means of weight loss, electrochemical polarisation and impedance techniques. A synergistic effect was observed when these two eco‐friendly non‐toxic inhibitors were used in protecting carbon steel. A non‐linear relationship existed between the concentrations of the two inhibitors showing a synergistic effect.

The inhibition efficiency of sodium gluconate (SG) in controlling corrosion of carbon steel immersed in the environment containing 60 ppm Cl^– has been evaluated in the presence and absence of Zn²⁺ by weight loss method. SG and Zn²⁺ show a synergistic effect. The protective film has been analysed by FTIR and fluorescence spectra. The protective film consists of Fe²⁺‐gluconate complex and Zn(OH)₂. The film is found to be UV‐fluorescent. The IE of the SG‐Zn²⁺ system increases in the presence of Na₂SO₄; but decreases in the presence of Na₂SO₃ and also in the presence of N‐cetyl‐N,N,N‐trimethyl ammonium bromide. This study reveals that the transporting phenomenon plays a larger role than the scavenging of dissolved oxygen.

Work has been performed to assess the corrosion inhibiting performance of a tertiary amine possessing two carboxylic acid groups (N coco‐amine‐2‐proprionic acid), on initially clean and pre‐corroded mild steel. Using linear polarisation and AC impedance high levels of efficiency were measured within the first hour of inhibitor addition at a concentration level of 10ppm. Simultaneously rapid anodic changes in corrosion potential were observed. With increasing pre‐corrosion decreased efficiencies were obtained, but still greater than 90 per cent, and this coincided with a less rapid alteration in steady state potential. The good response of the inhibitor has been attributed to the adsorption of negatively charged oxygens at the anodic sites on the metal surface, although pitting was detected once testing was terminated. Previously using inhibitors possessing positive charges (short and long chained quarternary amines), under the same environmental conditions, efficiencies > 90 per cent after the first hour were not achieved.

The inhibiting action of 2‐mercaptobenzothiazole (MBT) and cetyl trimethyl ammonium bromided (CTAB) on the corrosion of brass in groundwater have been studied by open circuit potential and potentiodynamic polarization techniques. The results revealed that the inhibition occurred by blocking the reaction sites on the surface of brass via chemisorption of the inhibitors. The adsorption of both the compounds on brass surface in groundwater is found to obey Langmuir isotherm. The results also indicate that MBT functions predominantly as an anodic inhibitor whereas CTAB and the combination of MBT and CTAB (MBT + CTAB) behave as mixed type inhibitors.