Insoluble Corrosion Products Research Articles

A comparison of runoff rates between Cu, Ni, Sn and Zn in the first steps of exposition in a French industrial atmosphere

The runoff rates of copper, zinc, nickel and tin were studied in a French industrial area for 161 days. The mass variation of the metallic coupons and the adherent corrosion layers were analysed at different time intervals, using a multianalytical approach. Atmospheric corrosion of copper is associated with the formation of a corrosion layer which is partly soluble in water, mainly composed of cuprite and basic copper sulphate salts. The corrosion of zinc is accompanied by the formation of a corrosion layer, partly soluble, containing mainly basic zinc carbonate and basic zinc sulphate salts. The behaviour of nickel exposed in an unsheltered atmosphere is characterised by a pitting corrosion process. Soluble corrosion salts such as nickel sulphates, chlorides and nitrates, formed during relative dry periods, are totally dissolved during rainfall events. The corrosion product of tin has been identified as a poorly crystallised hydrated stannic oxide. Depending on the solubility of corrosion products, the runoff rates appear to be different for these metals in the following order: zinc>copper>nickel>tin. Tin runoff rate is insignificant because of the insoluble corrosion products formed on the surface. This paper sets out a comparison between metal ions and anionic species found in the runoff water at various collecting period. The results revealed the runoff amount of copper, zinc and nickel released mainly from the dissolution of soluble sulphate compounds present in the corrosion layers.

Surface layers on a borosilicate nuclear waste glass corroded in MgCl 2 solution

Surface layers on the French borosilicate nuclear waste glass, R7T7, corroded in MgCl 2 solution were studied to determine the composition, structure and stability of crystalline phases. The characteristics of the phases constituting the surface layer varied with the parameter S V × t , the glass surface area ( S) to solution volume ( V) ratio, times time ( t). At low S V × t values (< 360 days/m; ≤ 36 d) th surface layer was thin and contained mainly iron hydroxide particles and hydrotalcite crystals. At an intermediate S V × t value (2800 d/m; 5.5 y) the surface layer contained hydrotalcite-, chlorite- and saponite-type phases. At the highest S V × t value (10 7 d/m; 463 d) the major phases were saponite, powellite, barite and cerianite solid solutions. About 95% of the uranium and > 98% of the neodymium released from the glass were precipitated in the surface layer. In the 463 day experiment, 86% of the neodymium in the surface layer was in solid solution with powellite, the rest with saponite. Uranium was contained exclusively in saponite. High S V ratios, typical of disposal conditions for vitrified high-level radioactive waste, favor retention of actinides in fairly insoluble corrosion products. Observation of similar corrosion products on natural glasses as on nuclear waste glasses lend support to the hypothesis that the host phases for actinides observed in the laboratory are stable over geological periods of time.

Electrochemical behaviour of copper in neutral aerated chloride solution. I. Steady-state investigation

The electrochemical behaviour of a Cu rotating disc electrode in neutral aerated NaCl solution was investigated in the cathodic and anodic ranges and at the corrosion potential. In the cathodic range, where the reduction of oxygen takes place, reduction peaks allow the identification and quantitative evaluation of insoluble corrosion products (CuCl and Cu2O). In the anodic range Cu is dissolved, most likely as CuCl 2 − . A new mechanism for the anodic dissolution is proposed after comparing our data with previously published mechanisms. Corrosion currents were found to decrease with time and to be a function of the rotation rate of the electrode. Both the mixed kinetics of the anodic partial reaction and diffusion through a porous layer seem to be relevant in controllingl corr.

On the passivation of nickel in aqueous solutions - I. The identification of insoluble corrosion products on nickel electrodes using optical and ESCA techniques: by R.E. Hummel, R.J. Smith and E.D. Verink Jr. (pp.803–813, Vol. 27, No. 8)

On the passivation of nickel in aqueous solutions - I. The identification of insoluble corrosion products on nickel electrodes using optical and ESCA techniques: by R.E. Hummel, R.J. Smith and E.D. Verink Jr. (pp.803–813, Vol. 27, No. 8)

Corrosion of Metals by Nitric Acid-Dinitrogen Tetroxide-Fluoride Mixtures: AISI 321 Stainless Steel

Abstract The inhibiting effect of fluoride on the corrosion of AISI 321 stainless steel (SS) by mixtures of 100% nitric acid (HNO3) and dinitrogen tetroxide (N2O4), used as the oxidizer components of liquid rocket propellants, has been investigated, with particular regard to the influence of the N2O4 content of the mixture and the nature of the solid corrosion products formed in such systems. It has been established that the effectiveness of fluoride inhibition in these mixtures decreases with increasing N2O4 content and, for one of these N2O4 mixtures [high-density (nitric) acid (HDA)], with increasing water concentration. Investigation of the surface film formed on AISI 321 SS in the latter mixture has shown it to be primarily an oxide layer but some fluoride is incorporated also. It has been found that the long-term storage of fluoride-inhibited HNO3-N2O4 mixtures in contact with AISI 321 SS results in the eventual precipitation of an insoluble corrosion product identified as a previously unknown hydra...

The passivation of nickel in aqueous solutions—I. The identification of insoluble corrosion products on nickel electrodes using optical and ESCA techniques

In situ differential reflectometry in conjunction with ESCA techniques are used to identify various surface films which form electrochemically on nickel. The film observed on pure Ni in a 0.15 N Na 2SO 4 electrolyte has been identified to be primarily Ni(OH) 2. At different values of pH and potential, NiO has been found to form simultaneously with Ni(OH) 2. At solutions with pH > 8, the Ni(OH) 2 film partially transforms into a third oxide, presumably NiOOH, which can only be observed in situ.

The Effect of Ammonium Chloride and Fluid Velocity on the Corrosion Behavior of Copper in Sodium Bicarbonate Solutions

Abstract The effect of ammonium chloride additions on the corrosion behavior of copper in 1 N sodium bicarbonate solutions has been characterized using a rotating ring-ring linear cyclic voltammetry technique. The experimentation and solution compositions used were selected to account for an unusually high incidence of pitting found to occur on interior surfaces of copper cold-water plumbing fixtures in the vicinity of neutral soldering flux residues. Although concentrations of ammonium chloride above 0.05 N were found to result in an increase of corrosion rate often attributed to the stabilization of a cuprous ion complex metal dissolution reaction product, under freely corroding conditions in an air-saturated solution, corrosion of copper metal would occur by an anodic process in which current was distributed between both soluble metal ions (cuprous and cupric ions) and insoluble corrosion product deposits. Although increases in applied potential or relative fluid velocity produced increases in the total corrosion rate, there was also a change in current distribution between the various components of the overall anodic process. Results from this study suggest that soluble and insoluble corrosion products (cathodically or anodically generated during a single linear polarization cycle) affect corrosion behavior during either successive cycles or extended exposure periods to such an extent that sole reliance on single-cycle anodic polarization behavior for the prediction of long-term corrosion resistance for copper and its alloys should be avoided.

The role of wedging stresses in the exfoliation corrosion of high strength aluminium alloys

The wedging stresses generated by the formation of insoluble corrosion products have been measured during the exfoliation corrosion of the high strength aluminium alloy L95. Stress intensity values obtained from double cantilever beam experiments, mathematical modelling and from observations of crack opening displacements are discussed with reference to the corrosion process. Exfoliation has effectively been prevented by applying compressive loading and it has been concluded that the degradation occurs by a stress corrosion mechanism.

Radiation chemistry related to nuclear power technology

A brief review is given to the radiation chemical problems, especially with the emphasis on water radiolysis, in the nuclear power technology. Radiation chemistry in aqueous system is pointed out to be closely related to the problems such as corrosion of Zircaloy, the formation of insoluble corrosion products or crud, stress corrosion cracking of stainless steel in BWR and the radioactive waste managements. The results of the constant extention rate tests on sensitized 304 stainless steel under irradiation are shown, and the computer calculations were carried out to simulate the model experiments on the release of crud from the corroding surface under irradiation and also the water radiolysis in core of BWR.

The use of controlled copper dissolution as an anti-fouling system

The use of copper as an anti-fouling surface is discussed and an electrochemical method for improving its performance is proposed. Seawater exposure trials of freely corroding, cathodically protected and electrochemically controlled copper specimens are described. The results show that the anti-fouling performance of copper surfaces may be improved by electrochemical control of its dissolution rates. The ultimate failure of the copper to anti-foul is due to insufficient dissolution rates. This may be due to electrochemical constraints, to the formation of insoluble corrosion products or to the precipitation of cathodic chalks at its surface.

Evaluation of Metallic coatings as related to their corrosion Resistance. A Review

An important difference between metallic and nonmetallic coatings is that the former can significantly affect the corrosion behaviour of the coated metal at sites where the coating is incomplete or damaged whereas generally organic coatings have no such effect. Metallic coatings afect the behaviour of the basis metal because an electrolytic cell is established in which either the basis or the coating metal will act as an anode and corrode at an enhanced rate. When the coating is the anode the basis metal will form the cathode and usually will corrode at a lower rate than in the complete absence of the coating. However, it is well known that simple considerations of anodic and cathodic behaviour do not explain all the phenomena involved in the corrosion and protection of metal coated metals. Other factors of importance include the formation of insoluble corrosion products and the influence of time and temperature on this process, the electrochemical polarisation behaviour of the metals, and the nature of the corrosive or inhibitive environment. The uses and properties of some types of metal coatings will be described in relation to these factors and the implication of these to test methods discussed. One particular system viz. galvanised steel in water containing a corrosion inhibitor will be described in more detail in terms of electrochemical behaviour.

Model Boiler Inhibition Studies of the Nuclear Steam Generator Denting Phenomenon

The buildup of an insoluble corrosion product in the annulus between the tube-to-tube-support-plate in some operating nuclear steam generators has resulted in a deformation or “denting” of the heat transfer tubes. A series of tests were initiated in single-tube model boilers to investigate the denting corrosion process and to determine additives and practices that would arrest this corrosion process. Test results show that properly administered additions of boric acid, sodium phosphate, or calcium hydroxide are capable of stopping the corrosion process leading to denting. Furthermore, it was determined that additions of either boric acid or lithium borate are effective in dent prevention, and this was demonstrated by adding contaminants and inhibitor simultaneously to a nondented test specimen.

Effect of Gamma Radiation on the Release of Corrosion Products from Carbon Steel and Stainless Steel in High Temperature Water

The effect of gamma irradiation on the release of the soluble and insoluble corrosion products was investigated with carbon steel and austenitic Type 304 stainless steel at high temperature using a...

The behaviour of ruthenium anodes in base

Cyclic voltammograms were recorded for ruthenium metal in base as a function of sweep limit and hydroxide ion concentration. A variety of both soluble and insoluble corrosion products were observed and an attempt was made to identify the various processes taking place on the basis of known data for this system. The development of a charge storage film under potential cycling conditions, as on iridium and rhodium, was noted. Current flow under potentiostatic conditions below 2.2 V was attributed largely to metal corrosion, the overpotential for oxygen evolution, which was observed only at higher values, being unusually high under these conditions. The vast difference in corrosion behaviour and rates of oxygen evolution between thermally and anodically prepared ruthenium oxide films was attributed to stronger bonding of surface ruthenium ions in the case of the thermally treated lattice. The pronounced effect of stirring on the anodic reactions of the metal in base was attributed to rapid removal of the weakly adherent surface oxide layer.

Copper Corrosion: II . Kinetic Studies

Experimental methods are described for studying rates of formation of soluble and insoluble corrosion products of copper exposed to water containing dissolved oxygen and carbon dioxide. Coulometric reduction indicates that the films formed on copper under these conditions are predominantly of cuprous oxide. Generation of cupric bicarbonate in solution and film growth are constant in rate over long periods, and both are kinetically of first order with respect to dissolved oxygen. Dependence of these rates on the concentration of dissolved carbon dioxide follows no obvious kinetic law, but is such as to suggest that the initial pH of solution is a major factor. Experiments in which either solution or metallic phase is replaced during kinetic measurements demonstrate that a cuprous oxide film on copper may have either an activating or a passivating effect, depending on its mode of generation. The evidence indicates the existence of an electrochemical mechanism for general corrosion of copper by which dissolution and film growth are kinetically linked processes.

The Separation and Radioactive Assay of Fission Products From Samples Obtained From High-Temperature Pressurized-Water Loops

Summary Two radiochemical separation procedures for the analysis of samples from the pressurized-water loops at Chalk River are presented. A description is given of a typical loop and the associated sampling facilities, which include autoclaves for activity deposition and corrosion samples, hot and cold probes for filtering out insoluble materials in the loop water, and ion-exchange columns for use in determining soluble and insoluble activities in the loop water. A number of different types of samples are obtained from these facilities. The types of samples and the various methods of attack which are used to convert the samples to a form suitable for analysis are described. In the first method, the separation of Ru, Ce, Ba, Sr, I, Te, Zr and Mo from samples such as loop water, crud (insoluble corrosion products), etch solutions from metal specimens, and ion-exchange resins is described. This method is applied to crud or resin samples after decomposition by an alkaline fusion, or to water or etch-solution samples after digestion with an NaOH-Na 2 CO 3 solution. The attack is carried out in the presence of carriers. An initial separation of the fission products is effected by boiling the alkaline carbonate solution from the liquid samples with HIO 4 or leaching the solidified melt from the fusion with water. Under these conditions, Ru, I and Mo are soluble, while the other elements are present as insoluble hydroxides, carbonates, or sulfates. The two fractions are separated into the individual components by normal chemical methods. The individual components are then purified by modified standard procedures which are described. In the second method, the separation of fission gases from loop water is described. No chemical separation of the mixture of gases is carried out. The assay of the individual elements and nuclides is based on the careful choice of time intervals for the various steps in the initial separation and for counting the individual nuclides. Further separation is obtained by the use of differential γ - ray counting to select various nuclides for counting at set time intervals after sampling. Fission products from the first separation were mounted on flat filter paper sources and counted by beta proportional counting, either directly or through absorbers. Details are given of the counter and the mathematical methods used to compute absolute disintegration rates. The gases, as has been mentioned, were determined by differential gamma counting. A full description is given of the counting equipment and the sample containers. The theoretical and practical details relative to the energies counted and the time intervals between counts are given, together with the mathematical methods necessary for calculating the results.

Accelerating Effect of Decreasing Temperature On Corrosion by Glycol Solutions

Abstract The corrosion of galvanized steel in solutions of ethylene glycol containing borax is found to increase with decreasing temperature. This is believed to be due to the formation of a soluble complex zinc salt, the stability of which is greater the lower the temperature, which prevents the formation of a barrier film of insoluble corrosion product. Cadmium, magnesium and brass are attacked at low temperature in glycol-borax solution by the same mechanism, as is zinc in solutions of glycol containing sodium acetate or sodium benzoate.