High temperature corrosion, at 730° C, by combustion gases produced by burning liquid fuels in a laboratory combustor has been investigated. A selected range of steels and alloys (mild steel, stainless steel type 347, Nimonic N90, N105, and IN657) have been tested in the combustion gases using fuels containing varying amounts of impurities in the range of 0 - 6% sulphur, 0 - 60 ppm sodium, and 0 - 300 ppm vanadium. On the basis of the comprehensive results a computer programme was written to predict corrosion rates of mild steel by combustion gases produced by burning fuels containing impurities such as sulphur, sodium and vanadium. The programme was tested, and the predictions which included the change of fuel were experimentally verified. Oil soluble additives have been used to show the effect on corrosion rates of the materials tested. By using X-ray diffraction analysis of the oxide layers, and with the help of electron microscopy, an attempt was made to investigate the mechanism of corrosion in the individual and collective presence of sulphur, sodium and vanadium-supplied by the test fuels. It is shown, for example, that the presence of sulphur in the fuel helps in the formation of FeO in the surface oxide layers. The ignition delay time or simply the ignition delay, which is the time lapse between the introduction of a fuel droplet into a heated atmosphere and its eventual ignition, was measured for all the test fuels. It is shown that the addition of elemental impurities such as sulphur sodium and vanadium have no significant effect on the ignition delay of the fuel but the addition of oil soluble additive makes the, ignition delay - temperature, curve steeper at the operating temperature and also reduces, corrosion of materials. Light hydrocarbon fuels having lower ignition delay than Kerosene at the operating temperature can be used as an additive to reduce the formation of sulphur trioxide in the combustion gases.

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Internal Corrosion of process pipework is a significant problem in many Chemical Industry scenarios, affecting plant integrity and profitability. It is vital that vulnerable sections of plant are monitored for corrosion on a regular basis and there are many established methods for so doing. The majority of these methods are intrusive in nature and those that are not either require considerable specialist expertise in their operation or require that the plant be shut down while monitoring takes place. This thesis explores the possibility of using non-intrusive, passive acoustic monitoring as a method of corrosion monitoring. Acoustic measurementsm, ade in the range 0- 20kHz, coupled with Chromaticity based Data Analysis Techniques have been shown to yield Acoustic Signatures, the variable nature of which can be used as an analysis tool for various aspects of plant operation. Measurements have been made on a Liquid Flow Rig, which was designed to mimic a section of a typical industrial process plant. Acoustical Characterisation of the rig was performed and was followed by a series of experimental measurements using Simulated Corrosion pipe inserts. It was found that the rig exhibited a complex acoustical behaviour and that the reproducibility of measurements made at low frequencies was generally poor. However, selection of a suitable Frequency Measurement Band, coupled with the use of appropriate Chromatic Filters has been shown to yield results that enable the corrosion state of the rig to be quantified. Additionally, it has been proved possible to monitor, quantitatively, other aspects of the rig, such as the degree of Cavitation and the condition of the Re-circulating Pump.

Sodium silicate solution (or water glass, WG) activated slag is one of the potential alternatives to 100% replace PC. WG activated slag concrete has different pore solution composition from that of PC. This could result in different chloride transport and corrosion of embedded steel for such concretes. In this research, chloride transport and resulting corrosion of steel in 12 WG activated slag concretes with Na20% of 4, 6 and 8 and Ms of 0.75, 1.00, 1.50 and 2.00 were investigated. PC concrete with the same binder content of 400kg/m3 was studied as a reference. The results showed that the corrosion rate of the steel in the WG activated slag concretes was comparable or even higher than that of the PC concrete irrespective of the lower chloride diffusivity of the former. The WG activated slag concrete with the combination ofNa20% of 6% and Ms of 1.50 gave the lowest chloride diffusivity and corrosion rate. Chloride migration coefficient, ASTM C 1202 charge passed and bulk electrical resistivity had a poor correlation with non-steady state chloride diffusion coefficient for WG activated slag concretes. The criteria of macro cell corrosion current and half-cell potential developed in PC may be not suitable for quantifying and qualifying corrosion activity of the steel in such concretes. The WG activated slag concretes were identified to be not suitable in chloride exposures XS3 and XD3 by considering workability, compressive strength, pore solution composition and corrosion rate.

In the UK, approval of stainless steel products by the Drinking Water Inspectorate invokes the Operational Guidelines and Code of Practice for Stainless Steel Products in Drinking Water Supply (OGCP) t Munro et al., 2002). Type 304L and 316L stainless steel grades can be used for the majority of applications in water treatment and supply, with the grade selection depending on the chloride and chlorine levels in the water. Currently the guideline suggests that 304L may be used up to 200 ppm chlorides and 2 ppm free chlorine and type 316L up to 1000 ppm chlorides and 5ppm free chlorine at pH levels greater than 6. Although the maximum chloride levels have been well researched and in most applications has supported this for many years, chlorine values are based on limited evaluations and, although they work well in most, more research is required to more closely define them. The purpose of this research is to understand and determine to what extent residual chlorine level, chloride content, and pH will affect the crevice corrosion behaviour of types 304L and 316L stainless steels in particular, and the initiation of crevice corrosion. The study required the creation of a controlled chlorinated system exposing creviced specimen using the multi-crevice assembly technique. The assemblies were immersed for 60 days at 20°C in chloride levels ranging from 200-2000 ppm, residual chlorine levels ranging from 0-10ppm; all at pH 6 and 8 . A fter the immersion period, specimens were investigated by visual examination, Scanning Electron Microscopy (SEM) and Atomic Force vlicroscopy (AFM). Potentiodynamic polarization studies were also 4 carried out for each of the environments. Custom made software programs were developed to analyse the data collected from SEM and AFM results to give a better understanding and clarification of the crevice corrosion phenomena, in each individual condition and to provide more confidence in the selection of chlorination levels for particular chloride water contents. From visual and optical assessment results presented that the earliest noticeable of crevice corrosion had occurred at 0 ppm chlorine, 1000 ppm chloride ppm, pH 6 and 20° C and at 2 chlorine ppm, 1000 chloride ppm, pH 8 and 20° C for 304L specimens while for 316L specimens no significant change was observed. These results supported with OGCP and showed that both type of specimens can be used at slightly higher concentrations of chlorine and chloride than the guideline values depending on how to keep the constant concentration and how much of the surface quality of specimens that will be used throughout the process . . -\FM and SEM results showed that corrosion surface activity had occurred on both 304L and 316L specimens, even the least aggressive chloride and chlorine concentrations. The corrosion surface activity IS proportional to the increase in the chloride and chlorine concentrations. Potentiodynamic polarization curves supported the evidence from AFM and SEM results that chemical activity inside the pit had occurred even at milder concentrations. Cr and Fe were oxidised as 02- and OH- penetrated into the pits. These electron exchanged of these chemical species had been interpreted by polarization curve which showed various 5 stages of these reactions (cathodic reaction, anodic reaction. passive stage and breakdown). The results showed that breakdown potential (Eb) and passive stage are inversely proportional to chloride and chlorine concentrations. The chlorine and chloride concentrations had a more dominant effect than pH especially at high concentrations due to the amount of chemical species inside the pit and electrolyte solution overcome pH effect and the process was under mass transport controlled until pH effect can be neglected. The custom made software offered more clarification of pit characteristics and shapes which will be useful in connected with corroded area and volume calculated and further study or future prediction of characteristic of crevice corrosion that will occur or likely to in different environments.

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