CORROSION RESEARCH ROUND‐UP

Abstract

Brightening solutions for aluminium. The chemical brightening of aluminium in mixtures based on phosphoric acid formed the subject of a series of experiments in which commercial purity aluminium panels were used in order to assess the influence of the aluminium content of the bath, and the effect of temperature upon the amount of metal removed. Four mixtures were employed: phosphoric‐sulphuric acid, phosphoric‐sulphuric‐nitric acid, phosphoric‐acetic‐nitric acid and phosphoric acid‐water‐nitric acid. If a highly specular finish is required, then the presence of about 5% (by volume) of nitric acid is essential. Acetic acid reduces the tendency for the rate of attack to increase with temperature, while water increases the maximum aluminium content which can be tolerated before the bath becomes unusable. Weight loss‐time curves are given for S1, S1B, S1C, NS4, HS10WP, HS15W and an Al (99.99%), 1.25% Mg, alloy treatment times up to 5 min. in the four solutions investigated. Except for HS15W, the response was found to be good for most materials, but a loss of brightness occurred with the lower‐purity materials on anodising.— (A. W. Brace and T. S. de Gromoboy, Trans. Inst. Met. Finishing, 1956, 33, advance copy No. 2.)

Citation

(1956), "CORROSION RESEARCH ROUND‐UP", Anti-Corrosion Methods and Materials, Vol. 3 No. 6, pp. 204-207. https://doi.org/10.1108/eb019190