Solid State Phenomena Vol. 227

Abstract: Although much less investigated than that induced by chlorides, the corrosion of steel reinforcing bars due to bacteria metabolic products is recognised as a serious issue, primarily for concrete pipes in sewer network. In order to overcome the complications due to the preparation of concrete samples the investigation was performed using simulating solutions. The passivation of the metallic specimens was obtained by immersion in Ca (OH)_{2 sat} and monitored through several different electrochemical techniques. The depassivation was induced by either sulphuric acid or sulphides in order to simulate different bacterial metabolites. Anodic polarization curves and optical microscopy examination revealed a significant corrosion in the former case, while a competitive interaction among the sulphide and the alkalinity was hypothesized in sulphide-containing solutions.

Abstract: The paper deals with the comparative study of bio-corrosion of fibrous cement boards and Portland cement composites. Fibre-cement flat boards are widely used materials in the Slovak Republic for exterior and interior cladding, as fibre-cement slates for roofing and cladding and as fibre-cement corrugated sheets for roofing and cladding. Bio-corrosion of studied materials has been simulated in laboratory conditions during 80 days. Effect of sulphur-oxidizing bacteria Acidithiobacillus thiooxidans on the specimens was investigated. The bio-deterioration processes have been manifested by leaching of main cement components as well as by surface changes. The calcium and silicon contents in leachates were evaluated during the experiments using X – ray fluorescence method (XRF). Concluding the results of the concrete’s biodeteriogens influence on the analyzed samples (fiber boards and cement composites) more extensive leaching of calcium ions from the cement matrix was confirmed as assumed by bacteria influence when compared to the abiotic environment. Mixture of white compounds on the samples surface was identified by SEM microscopy and XRD analysis as sulphate products (ettringite, thaumasite, gypsum). Shift of pH of liquid media to alkaline region up to 7.2 due to alkaline products leaching were noticed for all studied samples.

Abstract: High temperature sulphide corrosion and equipment failures have been reported in several crude and condensate processing facilities of petroleum refineries. Affected materials were carbon and low alloy steels operated in temperatures ranging from 200 to 300°C.These failures were attributed to specific sulphur species and were not anticipated by corrosion prediction tools used for their material selection. The corrosion mechanisms of these species are not fully understood. This paper presents Takreer Research Centre (TRC) research work for isolating the active sulphur species responsible for the corrosion. Two condensate samples were first analysed for total sulphur, hydrogen sulphide (H₂S), Mercaptans (RSH) and other impurities. Using Gas Chromatograph with Sulphur Chemilumenesence Detector (SCD), it was possible to identify Mercaptans and sulphides from the process samples. Laboratory corrosivity testing of condensate sample using carbon steel and low alloy steel coupons at 275°C indicated that the corrosion rate was mainly related to the Mercaptans species within the Total Sulphur. The results concluded that specific dissociation temperature of respective Mercaptans is a useful tool in predicting the possibility and extent of corrosion and its vulnerable process loop.

Abstract: The standard ISO 14713-1 shows that HDG coatings should protect steel in the corrosive atmosphere C5 for 10–21 years. It was observed that pitting corrosion appears already after 2–3 years on roads and urban infrastructures and both Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) have shown that lead inclusions were present in all such corroded zinc coatings. The laboratory prepared HDG coatings with different amount of lead inclusions were investigated by gravimetric method (after exposure in salt chamber), SEM with EDS, and Glow Discharge Optical Emission Spectrometry (GDOES). The corrosion resistance was analyzed in the polarization tests and local probe techniques. The inclusions could accelerate coating corrosion because lead is cathodic to zinc.

Abstract: Consequence assessment is an integral part of the risk assessment process. There are many types of consequences loss due to pipeline failure such as asset loss, environmental loss, production loss, and human health and safety loss (HHSL). This paper studies the comparison of HHSL between rural and urban areas due to pipeline failure subject to corrosion. The damage area of the explosion was calculated using Aloha software by considering the details of the selected sites such as atmospheric and topographical conditions. The HHSL was calculated using a mathematical equation of quantitative risk assessment in terms of the number of fatalities or injuries or both. The results of the assessments from rural and urban areas were then compared with one another to identify any significant dissimilarity. This study shows that there was a possibility to improve the decisive value of risk by implementing the proposed approach in consequence assessment in Malaysia.

Abstract: In this paper, a qualitative consequence assessment method for damaged urban natural gas pipelines is proposed. It focuses on identifying reputation loss factors according to stakeholders’ (investors, customers, employees, and communities) perceptions. The analytical hierarchy process (AHP) method is applied to prioritize these factors. Results show that the loss of customer confidence ranks as the highest contributor to an operator’s reputation loss due to a pipeline accident. Thus, better risk assessment of pipeline damage due to corrosion will be achieved with the inclusion of reputation loss in the consequence assessment. Hence, decision making in pipeline repair, inspection, and maintenance can be improved as well as a company’s annual profit margin.

Abstract: In our investigation we focused on effects of the degradation of Pt-Rh gauzes from three different industrial catalytic systems. The aim of the study was to compare the degree and the mechanism of degradation under different conditions (pressure, temperature, gas flow direction). The investigation was performed on about 80μm diameter wires after long (6 months) exposition to chemically aggressive environment. Microscope observations and microtomography analysis showed that all wires surfaces were strongly developed by etching and deposition processes occurring under extreme conditions. Each wire differed in rate of degradation and morphology of the characteristic cauliflower-shape growths. Also differences in elements distribution on both, surface and cross sections, were observed. Obtained results can be basis of further investigation on improvement of endurance of PtRh alloys in high temperature chemical application.

Abstract: After over 16 years long service on the inner walls of a steel absorber and outlet channel in wet FGD system, the rubber lining was subjected to examinations. A series of impedance spectra for the pre-vulcanized soft rubber lining based on chlorobutyl rubber (CIIR) were recorded. Rubber lining samples taken from the absorber bottom, which had been in contact with the washer sump solution, exhibited properties similar to those of new rubber lining samples not exposed to the corrosive environment. Rubber lining samples taken from the absorber upper part and from the outlet channel showed significant damage, and so deterioration in their protective properties, in comparison with the new lining. Also the results of tensile strength and hardness tests carried out on rubber samples taken from various parts of the absorber and the outlet channel are presented.

Abstract: It is known that load-bearing metallic structures that are in service in the atmospheric conditions showed that are exposed to corrosion. The known-in-the art paint-and-lacquer protective coatings can provide protection of metal surfaces for a rather short period between 5 to 10 years. That is why these structures should be protected by the more advanced coatings of new generation, namely: geocement-based coatings which differ from the known-in-the-art binding materials by formation in the hydration products of the zeolite-like minerals and feldspathoids. The paper discusses substantiation of choice of geocement composition in the (хК, уna)₂O⋅Al₂O₃⋅nSiO₂⋅mH₂O system, target synthesis of hydration products of the geocements matrix in the fields of dynamic cavitation, optimal parameters of cavitation treatment aimed at nanostructurization of the geocements matrix in order to synthesize zeolite-like and hydromicaceous phases, choice of appropriate hardening agents and fillers etc. for producing highly efficient protective coatings with high corrosion resistance, high adhesion to metallic substrate and durability.

Abstract: High dispersed nano and micro particles as ceramics (SiC, TiC, WC, Al₂O₃), polymers (UHMWPE) or bioceramics (TiO₂, CeO₂, ZrO₂) have been deposited by electrochemical method with nichel or cobalt on metallic substrate to obtain novel structured composites, cermet or hybrid coatings with specific properties to be used in industrial or biomedical applications. The industrial applications for metal matrix based nanocomposites are increasing and open a way to biocompatible coatings. electrodeposition is considered to be one of the most important techniques for producing nanocomposites and nanostructured surfaces. Electrodeposition is exceptionally versatile, so that new and exciting applications are still being invented. The paper presents some results regarding the electro-co-deposition of dispersed phases as ZrO₂, CeO₂, SiC, WC, TiC or polymeric dispersed phases as UHMWPE (ultra high molecular weight polyethylene) during cobalt or nickel electroplating process in view of obtaining new advanced functional surfaces with improved properties to corrosion or tribocorrosion systems.