Identification and Characterization of Nonchromate Corrosion Inhibitor Synergies Using High-Throughput Methods

• Published in: Corrosion (Houston, Tex.) Vol. 64; no. 3; pp. 255 - 270
• Main Authors: TAYLO, S. R, CHAMBERS, B. D
• Format: Conference Proceeding Journal Article
• Language: English
• Published: Houston, TX NACE International 01.03.2008
• Subjects: Aluminium; Aluminum; Aluminum base alloys; Applied sciences; Barium; Cerium; Chloride; Chromate; Chromates; Corrosion; Corrosion environments; Corrosion inhibitors; Corrosion prevention; Direct current; Electrochemistry; Electrode polarization; Europium; Exact sciences and technology; Experimentation; Gadolinium; High-throughput screening; Identification; Identification methods; Inhibitors; Lanthanum; Lanthanum chlorides; Metals. Metallurgy; Molybdate; Neodymium; Phosphates; Potassium; Potassium phosphate; Potassium phosphates; Sodium; Sodium chloride; Sodium molybdate; Sodium phosphate; Sodium silicates; Testing; Trisodium phosphate; Yttrium; Cyclic voltammetry; Aluminium base alloys; Corrosion; high-throughput screening; inhibitor synergy; AA2024-T3; Corrosion protection; corrosion inhibitors; fluorometric probes; nonchromate inhibitors; Corrosion inhibitor
• ISSN: 0010-9312; 1938-159X
• DOI: 10.5006/1.3278470

The replacement of chromate corrosion inhibitors will require synergistic combinations of materials that can only be identified and characterized through experimentation at the present time. One approach to accelerate the discovery and characterization of materials is through the use of high-throughput screening (HTS) methods. This paper presents three methods developed for the HTS of corrosion inhibitors and their combinations for the aluminum aerospace alloy, AA2024-T3 (UNS A92024). Rapid assays for corrosion determination included direct current (DC) polarization, surface copper assessment, and fluorometric detection of Al3+. These methods increased experimental throughput by a factor of more than 1,000. Tests were conducted on single and binary combinations of cerium chloride (CeCl3), yttrium chloride (YCl3), lanthanum chloride (LaCl3), europium chloride (EuCl3), gadolinium chloride (GdCl3), neodymium chloride (NdCl3), sodium metatungstate (NaWO4-3WO3), sodium metavanadate (NaVO3), sodium molybdate (Na2MoO4), sodium metasilicate (Na2SiO3), potassium phosphate (KH2PO4), sodium phosphate (Na3PO4), and barium metaborate (BaB2O4). Testing was performed at 3.4 mM total inhibitor concentration in 0.6 M sodium chloride (NaCl) at pH 2, 4, 7, 10, and 12. The results from each HTS assay correlated well with 10-day electrochemical impedance target data (R2 = 0.80 to 0.90). HTS testing revealed both synergistic and antagonistic pairings of the inhibitors. Synergistic combinations have been identified with corrosion inhibition properties that exceed those of chromate under the conditions of these HTS methods. These methods provide a promising route for the rapid discovery and characterization of effective nonchromate corrosion inhibitors and other electrochemical phenomenon.