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This study aims to investigate the initial corrosion behavior in aqueous solution of 20# seamless steel under (CO₂/aqueous solution) gas–liquid two-phase stratified flow conditions.

The initial corrosion behavior was studied through the weight loss methods, scanning electron microscopy with energy-dispersive x-ray spectroscopy and x-ray diffraction.

The corrosion rate of 20# steel obviously increases with the increasing gas pressure at different corrosion time when the CO₂ pressure is less than 0.11 MPa, and the increase of corrosion rate tends to be steady when the pressure exceeds 0.11 MPa. With the increase of CO₂ pressure, the corrosion products changed from flocculent to acicular, granular and scaly. A four-stage model for the growth of the corrosion product layer was proposed, namely, the diffusion reaction stage, the local film formation stage, the complete film formation stage and the densification stage of the product film.

A four-stage model for the growth of the corrosion product layer on the pipe wall surface under this condition was proposed, namely, the diffusion reaction stage, the local film formation stage, the complete film formation stage and the densification stage of the product film. The growing process and densification mechanism of corrosion products layer were discussed.

This paper aims to synthesise anticorrosion pigments containing molybdenum for paints intended for corrosion protection of metals.

The anticorrosion pigments were prepared by high-temperature solid-state synthesis from the appropriate oxides, carbonates and calcium metasilicate. Stoichiometric molybdates and core-shell molybdates with a non-isometric particle shape containing Ca, Sr, Zn, Mg and Fe were synthesised. The pigments were examined by X-ray diffraction analysis and scanning electron microscopy. Paints based on an epoxy resin and containing the substances at a pigment volume concentration of 10 volume per cent were prepared. The paints were subjected to physico-mechanical tests and to tests in corrosion atmospheres. The corrosion test results were compared to those of the paint with a commercial pigment, which is used in many industrial applications.

The molybdate structure of each pigment prepared was elucidated. The core-shell molybdates exhibit a non-isometric particle shape. The pigments prepared were found to impart a very good anticorrosion efficiency to the paints. A high anticorrosion efficiency was found with the pigments Fe₂(MoO₄)₃ and Fe₂(MoO₄)₃/CaSiO₃ and with Mg and Zn molybdates.

The pigments can be used for the formulation of paints intended for the corrosion protection of metals. The pigments also improve the paints’ physical properties.

The use of the pigments in anticorrosion paints for the protection of metals is new. The benefits include the use and the procedure of synthesis of the anticorrosion pigments which are free from heavy metals and are acceptable from the aspect of environmental protection. Moreover, the core-shell molybdates, whose high efficiency is comparable to that of the stoichiometric molybdates, have lower molybdenum contents.

This study aims to investigate the inhibition performance of an aqueous extract of Matricaria recutita chamomile on the corrosion of S235JR steel in 0.5 M NaCl by using electrochemical impedance spectroscopy (EIS) and polarization measurements.

The inhibition performance was investigated using EIS and polarization measurements. Surface analysis demonstrates the presence of a protective layer on the steel surface in the presence of the extract. Quantum chemical parameters calculated for the molecules contained in the aqueous extract are interpreted to predict the corrosion inhibition efficiency of the considered extract.

The inhibition efficiency of chamomile aqueous extract for S235JR steel increases with increasing amounts of plant concentration and with an increase in the immersion time. The optimal inhibition efficiency of chamomile extract, 98.90 per cent, was achieved for S235JR steel when immersed in 15 per cent v/v of extract concentration for 2 h. The surface analysis in the absence and presence of the chamomile extract confirmed the formation of a protective layer on steel surface. The quantum chemical calculations allowed to explain the great inhibition efficiency values by interpreting the calculated quantum parameters.

This is the first study carrying out an experimental and theoretical investigation on M. recutita chamomile as a green corrosion inhibitor, with interesting potential industrial applications.

The paper studies the effect of modification of zinc orthophosphate on the anticorrosion efficiency thereof in organic coating. The zinc orthophosphate dihydrate and tetrahydrate and the reaction of phosphate anion with hydroxyl binder groups are compared. The highest anticorrosion efficiency is reached with pigments which are modified by organic corrosion inhibitors. The highly water soluble phosphate pigments reduce the anticorrosion coating properties. The effect of cation in phosphate pigments on the corrosion inhibition was confirmed.

The reliability and corrosivity of two VOC ‐ free, no‐clean fluxes (C and D) were assessed using traditional test method such as copper mirror and copper corrosion tests. Modified surface insulation resistance (SIR) tests using coupons fluxed with various methods were performed in 50°C/90%RH environmental conditions. Printed circuit boards and assemblies were fluxed and exposed to a 50°C/90%RH chamber to assess long‐term reliability. To evaluate the corrosion rates of copper and solder sheets in as‐ received liquid fluxes, electrochemical polarisation measurements were employed. These showed that the corrosion rate of copper in flux D is 100 times higher than that in flux C. These quantitative data agreed with the qualitative copper mirror test results, i,e, flux C passed and flux D failed the test. However, both flux residues were found to corrode copper traces underneath the solder mask and copper pads on the PCB after three weeks in a 50°C/90% RH environment chamber. Large amounts of blue/green corrosion products were observed on the bare copper SIR coupons within seven days when using either flux; and SIR values were below the required 10₈ ohms. Based on the test results, neither flux was qualified for no‐clean processes because of the issues with corrosion. The corrosiveness of the VOC‐ free, no‐ clean flux residue is believed to be due to the activator packages used.

Like aqueous corrosion of metals, atmospheric corrosion of metallic articles has also been a matter of great anxiety due to the individual and joint action of oxygen, humidity and various types of pollution gases and ions in the atmospheres. As there is no limit of oxygen availability in the open atmosphere, this type of corrosion of metals is mainly controlled by humidity. In industrial mines and marine environments, however, metal attack is controlled by aggressive gases, ions and chloride ions respectively.

This paper aims to provide an insight into the main parameters that govern corrosion mechanisms in production tubing of oil and gas wells.

Corrosion has been an old concern for the oil industry. None of the three major sectors of the oil industry, namely, upstream, midstream and downstream, are immune of corrosion attacks. However, the upstream sector (oil and gas production facilities) is more vulnerable to corrosion because of its extreme conditions such as high temperature and pressure, multiphase flow, complicated water chemistry, presence of acidic gases, etc. This paper is a general review of the influence of such parameters on corrosion mechanisms of oil and gas wells.

In recent years, many technical papers have been published in this area. However, none of them provide a general review of the all contributing parameters on corrosion under field conditions.

Modeling and corrosion mitigating processes under downhole conditions require a thorough understanding of the influencing parameters. This paper aims to provide an insight into the main parameters that govern corrosion mechanisms in production tubing of oil and gas wells.

To study the corrosion resistance of the novel alloy Al‐12.6La (wt%) manufactured using directional solidification.

Samples fabricated using the Bridgman growth technique at three different withdrawal velocities were subjected to total immersion tests in distilled water and in 3.5 per cent NaCl solution and to DC polarisation tests in distilled water. XPS analyses conducted on samples after polarisation indicated the presence of an La compound in the non passive corrosion products film formed.

Anodic polarisation induced dissolution of the alloy with the formation of a non passive corrosion product film. During potentiodynamic polarisation, a sudden current increment occurred at a potential value that was more positive for samples solidified at higher rates. The corrosion resistance of this Al‐12.6%La alloy decreased as the solidification rate increased.

The results presented in this work are an insight to the understanding of the corrosion resistance and electrochemical behaviour of this alloy for future engineering applications and development.

One of a series of papers presented at a Symposium “Designed with Thermal Spraying in the '80s” organised by the Association of Metal Sprayers at the Europa Hotel, London W.1 on 22 April, 1982.

The above Congress, being held at the Imperial College of Science and Technology, London, from April 10–15, has been described as likely to be the corrosion event of the decade. Size alone is no criterion, though over 80 papers are being presented, but the standing of many of the corrosionists associated with the Congress is, perhaps, the best indication of the truth of this statement. Summaries and abstracts of some of the papers appear in the following pages. More will be published in next month's issue.