ISSN 2305-6894

2014, Vol. 3, Issue 4 (pp. 215–306)

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VCI containing package material – mode of functioning

EXCOR Korrosionsforschung GmbH, Magdeburger Str. 58, 01067 Dresden, Germany

Abstract: I. L. Rozenfeld was one of the pioneers in the field of corrosion research and the application of vapor phase corrosion inhibitors (VCIs, volatile corrosion inhibitors). He found that no substance can sufficiently inhibit the corrosion by its own, what is reflected on conventional corrosion protection schemes. Nowadays, three strategies are established in the field of iron protection to reach a passive state: 1. the installation of buffer systems (combination of a weak acid with its corresponding base) to keep the pH value of the surface electrolyte layer constant in the alkaline range; 2. the combination of anodic and cathodic inhibitors to achieve a synergistic effect; 3. the supply of (at least one) oxidizing agent in the present of oxygen in the atmosphere or already dissolved in the surface electrolyte layer. In general, polymer ¬based packaging materials are used in order to protect metallic equipment (mostly made of iron materials) during transport and storage against atmospheric corrosion. This temporary corrosion protection is achieved by incorporation of VCI in the polymer film, whereby the packaging material functions as a VCI source. Protection is necessary especially during the time of wetness, where the metal surface can corrode due to the formation of a thin electrolyte layer on the surface. The efficiency of a selected combination of VCI compounds mainly depends on three parameters: 1. their vapor pressure (more exactly: their tendency to sublime) under atmospheric conditions are high enough allowing significant vapor phase transport of the compounds within an enclosed space to the metal surface; 2. their adsorption strength on the oxide covered metal surface (directly or after dissolving in the condensed water film) inhibiting the metal corrosion during storage and transport by interaction with the surface; 3. the achieved mixture of different VCIs on the metal surface to cover different strategies of corrosion protection Within this paper calculations should be presented to estimate the minimum need of VCI in dependence of the package volume, the surface roughness of the goods and the exposed temperature. Further, the transport of the VCI in the atmosphere of a densely closed package by diffusion and natural convection should be discussed. These findings can be used to approximate the conditioning time. In the second part results of electrochemical measurements like the measuring of the free corrosion potential and recording of electrochemical impedance spectra should be presented characterizing the interaction of different VCIs with oxide covered metal surfaces in the presence of a condensed air saturated water film. Thereby, mechanisms of action (e.g. passivation, adsorption and/or formation of insoluble salts to seal defects in the oxide layer) shall be derived from the data and compared to the concept of isoelectric points of metal oxides covered the metal surfaces (IEPS). Finally, the efficiency of VCI containing package materials should be demonstrated by self- developed climatic tests according to DIN EN 60068-2-30.

Int. J. Corros. Scale Inhib., , 4, 286–306 PDF (1 071 K)
doi: 10.17675/2305-6894-2014-3-4-286-306

Corrosion protection of flanges and valves

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1 Northern Technologies International Corporation, 23205 Mercantile Rd., Beachwood, OH 44122, USA
2 Astrakhan Gas Processing Plant, Astrakhan, Lenin St. 30, 414000 Russian Federation
3 VPK Engineering, Saint Petersburg, Tuchkov Per. 3, 199053 Russian Federation
4 Petrobras, República do Chile Av., Nr. 65, Rio de Janeiro – RJ, CEP: 20031-912, Brazil
5 ZERUST, Brazil, 1424 João Wagner Wey St. House 17, Sorocaba – SP, Brazil 18046-695

Abstract: Corrosion of pipeline flanges and valves is a major worldwide problem. These pipeline connections are highly susceptible to pitting and crevice corrosion, which is the primary cause of pipeline failure. Often, to reduce or eliminate the risk of leaks and the resultant problems (fire, explosions, environmental contamination, etc.), pipelines are taken out of operation. Many effective corrosion protection solutions exist, but none are universally applicable due to application limitations and/or cost. Over the last 10 years, we have developed different types of covers/systems that, when applied, provide efficient corrosion protection. This paper presents field trial test results over a one year period in a very harsh environment – at temperatures from –30 to +40°C and relative humidity higher than 50%. The new data demonstrates a high level of corrosion protection efficiency that allows to expand areas of flange savers application. This is an alternative, low-cost method which uses volatile corrosion inhibitors (VCI) to protect flanges, valves and welded joints from corrosion.

Int. J. Corros. Scale Inhib., , 4, 279–285 PDF (1 325 K)
doi: 10.17675/2305-6894-2014-3-4-279-285

Experiences on corrosion inhibitors for reinforced concrete

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Dipartimento di Chimica, Materiali e Ingegneria Chimica, "Giulio Natta", Politecnico di Milano, Via Mancinelli 7 Milano Italia

Abstract: Corrosion of carbon steel reinforcement is the most important cause of premature failure on reinforced concrete structures. Prevention of corrosion is primarily achieved in the design phase by using high quality concrete and adequate cover. Additional prevention methods are adopted when severe environmental conditions occur or on structures requiring very long service life. Among these methods, corrosion inhibitors seem to offer a simple and cost effective prevention technique. They may be used both as a preventative techniques, if added to fresh concrete, and as a repair system, if applied on hardened concrete. The performance of corrosion inhibitors for reinforced concrete structures affected by chloride induced and carbonation corrosion has been studied at PoliLaPP, Laboratory of Corrosion of materials “P. Pedeferri” of the Department of Chemistry, Materials and Chemical Engineering “G. Natta”, Politecnico di Milano, in the last 15 years. Organic commercial admixed corrosion inhibitors delayed the occurrence of chloride induced corrosion. This result is related to two effects: reduction of the rate of chloride transport into concrete and increase of the critical chloride threshold. Commercial migrating corrosion inhibitors (MCI) are able to delay time-to-corrosion of passive rebars in concrete subjected to chlorides ponding; this effect is mainly related to the reduction of chlorides diffusion coefficient. MCI can reduce the corrosion rate after corrosion initiation only in carbonated concrete, nevertheless efficiency is low and residual corrosion rate is not negligible. Commercial MCI can penetrate into concrete mainly through capillary sorption but penetration depth is limited to 20 mm. The results obtained with nitrite-based inhibitor confirm literature data: the inhibitor is effective if the molar ratio [NO2-]/[Cl-] is higher than 0.5–0.6; in carbonated concrete, due to insufficient amount of inhibitor, no significant effect has been observed on corrosion rate. Among the tested organic substances, compounds containing carboxylic group showed the best results solution tests: pitting potential, time-to-corrosion and critical chloride content are similar to those obtained with sodium nitrite. In concrete tests, only one amine and one amino acid showed good performance increasing the critical chlorides threshold with respect to the reference condition. For carboxylate substances, a strong link was found between inhibiting properties and molecular structure.

Int. J. Corros. Scale Inhib., , 4, 254–278 PDF (1 427 K)
doi: 10.17675/2305-6894-2014-3-4-254-278

Protection of low-carbon steel in phosphoric acid solutions by mixtures of a substituted triazole with sulfur-containing compounds

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

Abstract: Based on IFKhAN-92 inhibitor, which is a substituted triazole, and sulfur-containing additives, efficient mixtures have been developed that protect low-carbon steel in phosphoric acid solutions in a broad range of acid concentrations (2.0–8.0 M) and temperatures (0–95°C).

Int. J. Corros. Scale Inhib., , 4, 246–253 PDF (703 K)
doi: 10.17675/2305-6894-2014-3-4-246-253

On penetration of IFKhAN-80 migrating corrosion inhibitor into cement stone

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

Abstract: The penetration of IFKhAN-80 migrating corrosion inhibitor into cement stone was studied. It was found that the depth of steel reinforcement protection in concrete containing 3% NaCl (with respect to the binder) depends on the inhibitor dosage and application method and can be up to 15–20 cm. For practical use, the consumption rate of IFKhAN-80 will depend on the reinforcement depth but should not be lower than 0.6 L/m2.

Int. J. Corros. Scale Inhib., , 4, 238–245 PDF (393 K)
doi: 10.17675/2305-6894-2014-3-4-238-245

Inhibition of corrosion and hydrogen permeation into carbon steel in solutions containing hydrogen sulphide and carbon dioxide

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1 Derzhavin State University, ul. Internatsyonalnaya, 33, Tambov, 392000, Russian Federation
2 Russian Scientific Research Institute of Use of Machinery and Oil Products, NovoRubezhnyi per., 28, Tambov, 392022, Russian Federation
3 Tambov State Technical University, ul. Sovetskaya, 106, Tambov, 392000, Russian Federation

Abstract: The efficiency of ethoxy higher aliphatic amines (EOAs) against carbon dioxide and hydrogen sulphide corrosion and hydrogen permeation into carbon steel in acid solutions has been studied. The influence of the number of ethoxy groups (2, 5 and 14), the length of the hydrocarbon radical (R = C10 –C13 and R = C17 –C20), medium acidity (0.005–0.05 M HCl), and electrode potential was investigated. Concurrently, the influence of higher aliphatic amine bottoms (emulgin) that are a mixture of primary and secondary aliphatic amines was studied. The protective efficiency of EOAs reaches 95–99.9%, hydrogen permeation decreases both at the corrosion potential and under conditions of anodic and cathodic polarization of the steel electrode. The inhibiting effect of emulgin is 96–97%.

Int. J. Corros. Scale Inhib., , 4, 227–237 PDF (720 K)
doi: 10.17675/2305-6894-2014-3-4-227-237

The inhibitive effects of 8-mercaptoquinoline and its iron chelate complex in the acid corrosion of iron in 1 M HCl

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Southern Federal University, ul. Zorge 7, Rostov-on-Don, 344090 Russian Federation

Abstract: The inhibitive effect of a 8-hydroxyquinoline derivative (1) and the corresponding Fe2+ chelate (2) in the corrosion of Fe in 1 M HCl was studied. The adsorption mechanism of these compounds was considered and the post-treatment effect of these compounds was studied. An increase in the concentration of compounds 1 and 2 increases corrosion inhibition for all the compounds studied. The residual protective effect of chelates is much higher than that of the corresponding ligands. The results that we obtained were interpreted in terms of organic compounds – metal surface interactions.

Int. J. Corros. Scale Inhib., , 4, 215–226 PDF (868 K)
doi: 10.17675/2305-6894-2014-3-4-215-226

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