ISSN 2305-6894

2017, Vol. 6, Issue 4 (in progress)

Influence of melting and casting conditions on the structure
and properties of sacrificial anodes

      • V. Kechin1 and E. Lyublinski2
1Vladimir State University, ul. Gor’kogo, 87, Vladimir, 600000 Russian Federation
2COR/SCI, LLC, 6421 Dorset Ln., Solon, OH 44139, USA

Abstract: Broad application of aluminum, magnesium and zinc alloys used for production of cast galvanic anodes (GA) is well known in the systems for corrosion protection of metal constructions and structures in sea water, soil, etc. The main requirement of the standards for various brands of protective alloys is their chemical composition (content of alloying components and maximum permissible concentrations of major cathodic impurity elements) that defines the electrochemical properties of alloys (working potential, current output and capacity). In terms of industrial production any deviations of technological parameters for melting and casting, found in various combinations, have a negative impact on both content of the non-regulated impurity elements (dissolved hydrogen, oxide inclusions, etc.) and on the structural homogeneity of cast anodes. This explains the conflicting data about the effectiveness of individual cast anodes made from one alloy grade and even one melting. Based on theoretical and experimental research, the role of metallurgical (provision of specified chemical composition and purity of alloys) and technological (ensuring homogeneous cast structure) factors in changing the quality of cast anodes was found. To provide specified and stable protective properties of aluminum, magnesium and zinc sacrificial anodic alloys technological processes of melting and casting were developed, which take into account the physicochemical nature of alloys, as well as design, weight and dimensions of the cast anodes. Presented are the main properties of modified sacrificial anodic alloys in sea water and soil.

Int. J. Corros. Scale Inhib., 2017, 6, no. 4, 359-371 (PDF 1551 K)
doi: 10.17675/2305-6894-2017-6-4-1

Mixtures of substituted pyridinium perchlorates with sulfur-containing organic compounds as inhibitors of acid corrosion of steel

      • A.G. Berezhnaya, Gh.A.H. Shayea and V.V. Chernyavina
Southern Federal University, ul. Zorge 7, Rostov-on-Don, 344090 Russian Federation

Abstract: 2,4,6-Triphenyl-N-(4´-aminophenyl) pyridinium perchlorate (PP1) and 2,4,6-triphenyl-N-(2´-bromophenyl)pyridinium perchlorate (PP2), Thiourea (TU), phenylthiourea (PhTU), diphenylthiourea (DPhTU), sodium diethyldithiocarbamate (DEDTC), 2-mercaptobenzo¬thiazole (MBT), and mixtures of pyridinium perchlorates with sulfur compounds were investigated as corrosion inhibitors of steel in a hydrochloric acid solution at temperatures of 20–80°C. The concentration ranges of substituted pyridinium perchlorates and sulfur-containing substances were 0.01–0.5 and 0.1–10 mmol/l, respectively. The coefficients of mutual influence of additives in mixtures, the degree of protection and the coverage of steel surface with inhibitors were estimated. The effect of the investigated additives and their mixtures on the partial reactions of the corrosion process was determined. The mechanism of action of individual additives was determined.

Int. J. Corros. Scale Inhib., 2017, 6, no. 4, 372-383 (PDF 1450 K)
doi: 10.17675/2305-6894-2017-6-4-2

Organic corrosion inhibitors: where are we now? A review. Part IV. Passivation and the role of mono- and diphosphonates

      • Yu.I. Kuznetsov
A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninskii pr. 31, Moscow, 119071 Russian Federation

Abstract: This article continues the review of studies (2006–2016) dealing with the passivation of various metals by solutions of organic corrosion inhibitors. It provides an overview of papers on the passivating properties of mono- and diphosphonic acids and their salts. The results of corrosion and electrochemical studies, as well as studies on the composition and structural features of surface layers on metals by a variety of physicochemical methods are considered.

Int. J. Corros. Scale Inhib., 2017, 6, no. 4, 384-427 (PDF 1226 K)
doi: 10.17675/2305-6894-2017-6-4-3

Corrosion inhibition and thermodynamic activation parameters of Myrtus communis extract on mild steel in sulfamic acid medium

      • A.S. Fouda,1 S.A. Abd El-Maksoud,2 M.Sh. Zoromba2 and A.R. Ibrahim1
1Department of chemistry, Faculty of Science, Mansoura University, Mansoura-35516, Egypt
2Department of chemistry, Faculty of Science, Port Said and King Abdulaziz University, Port Said, Egypt and KSA

Abstract: The effect of an aqueous extract of Myrtuis communis on the corrosion behavior of mild steel (MS) in 5% NH2SO3H solution has been investigated by the following techniques: weight loss (WL), potentiodynamic polarization (PP), electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation techniques (EFM). The inhibition efficiency (IE) increased with increase in inhibitor dose and increased with rise in temperature. The thermodynamic parameters of corrosion and adsorption processes were calculated and discussed. The adsorption of this extract was found to obey Langmuir adsorption isotherm. The PP tests indicated that the extract is mixed type. The results obtained from the three different techniques were in good agreement. The morphology of the surface was analyzed and discussed.

Int. J. Corros. Scale Inhib., 2017, 6, no. 4, 428–448 (PDF 1226 K)
doi: 10.17675/2305-6894-2017-6-4-4

Protection of aluminium alloys from atmospheric corrosion by thin films of inhibitors

      • A.M. Semiletov
A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky pr. 31, Moscow, 119071 Russian Federation

Abstract: Some prospects for protection of aluminum alloys by corrosion inhibitors such as carboxylates and trialkoxysilanes are considered. The efficiency of inhibition of anodic dissolution of Al alloys by these compounds in a neutral borate buffer solution containing chlorides (pH 7.4) was investigated. The protective capability of the layers obtained was estimated by an express method (drop test method) and by tests in a heat and moisture cabinet, and in a salt fog cabinet. The efficiency of treatment of Al alloys by aqueous solutions of organic inhibitors was compared with the protective ability of chromate films. It is shown that the passivation of Al alloys by the composition of oleyl sarcosinate with aminoethylaminopropyl–trimethoxysilane at a ratio of 3:1 is an efficient protection method even under salt fog conditions.

Int. J. Corros. Scale Inhib., 2017, 6, no. 4, 449–462 (PDF 1057 K)
doi: 10.17675/2305-6894-2017-6-4-5