Publications

Bi-modal trends in the long-term corrosion of copper and high copper alloys

The evolution of corrosion loss and maximum pit depth of copper and copper alloys exposed for long periods of time in natural and industrial environments is shown to be more consistent with a bi-modal functional form than with the classical power law. Data from several long-term exposure test programs supports this proposition. The bi-modal behaviour signals a change from mainly cathodic oxygen reduction to a subsequent transitory corrosion process that may be modelled as involving pitting under earlier copper corrosion products. Possible reasons for some data sets showing decreasing maximum pit depths with increasing exposure time are discussed.

Failure Prediction of Mild-Steel Welds Due to Climate Change Influenced Marine Corrosion

No abstract is provided for this article.

Editorial overview

No abstract is provided for this article.

Role of Chlorides in Corrosion of Reinforcing Steel in Concrete

Chlorides have long been held responsible for the initiation and progression of the corrosion of reinforcing steels in concrete structures, with higher concentrations assumed to cause earlier and more severe subsequent reinforcement corrosion. However, extensive field observations and detailed experimental results show that, in well-compacted, low-permeability concretes, reinforcement corrosion often does not occur even in the presence of high concentrations of chlorides. If corrosion does occur, it has been observed as pitting (and crevice) corrosion primarily at air voids in the concrete at the steel–concrete interface. Herein, it is shown that this is consistent with thermodynamic principles (Pourbaix) for the pitting of steel in practical concretes with high pH and air voids, irrespective of chloride concentration. Any subsequent corrosion becomes inhibited, in part through the formation of corrosion products. The experimental observations also show that there is a separate, concurrent process of the dissolution of calcium hydroxide and its leaching from the concrete. The rate of dissolution is accelerated proportionally to the concentration of chlorides. This is the primary mechanism for longer-term reinforcement corrosion, eventually producing circum-neutral pH at the steel and thereby setting up the thermodynamics permitting general corrosion. The findings question the relevance of a critical chloride concentration as an indicator of the commencement of reinforcement corrosion. Concrete permeability, remaining alkali reserves (or pH), and physical observation of evidence of rust damage are better indicators.

Life‐Cycle Performance of RC Bridges: Probabilistic Approach

This article addresses the problem of reliability assessment of reinforced concrete (RC) bridges during their service life. First, a probabilistic model for assessment of time‐dependent reliability of RC bridges is presented, with particular emphasis placed on deterioration of bridges due to corrosion of reinforcing steel. The model takes into account uncertainties associated with materials properties, bridge dimensions, loads, and corrosion initiation and propagation. Time‐dependent reliabilities are considered for ultimate and serviceability limit states. Examples illustrate the application of the model. Second, updating of predictive probabilistic models using site‐specific data is considered. Bayesian statistical theory that provides a mathematical basis for such updating is outlined briefly, and its implementation for the updating of information about bridge properties using inspection data is described in more detail. An example illustrates the effect of this updating on bridge reliability.

New insights from probabilistic modelling of corrosion in structural reliability analysis

Infrastructure intended to contain or exclude fluids or gasses, or reinforced with glass or other fibres may be subject to failure caused by pitting corrosion of the containment system or of the reinforcement. To assess the reliability of the infrastructure then requires probabilistic models for the deterioration processes involved. Typically the critical deterioration is through localized pitting and in particular the most extreme pit depth as this governs containment capability and also fibre strength. The ‘arch-typical’ distribution for representing maximum pit depth is the Gumbel extreme value distribution, for which complying data plot linearly on a so-called Gumbel plot. However, there is increasing evidence that large, homogeneous datasets show significant deviations from linearity. This is demonstrated for steel plates continuously immersed in seawater, for the interior corrosion of water injection pipelines and for crude oil production pipelines. Further examples are given for the maximum pit depth on stainless steel rollers in the papermaking industry and for localized corrosion of glass fibre reinforcement in concrete structures. In each case the non-linear trends obtained permit a re-interpretation of, and new insights for, the underlying physico-chemical-material mechanisms. The results are important for accurate representation of deterioration processes and for best-practice structural reliability analyses.

Post-perforation external corrosion of cast iron pressurised water mains

The corroded external surfaces of older cast iron water mains buried in soils for many decades usually show a rough undulating topography. Sometimes, there also are areas of relatively smooth topography similar to uniform corrosion but over undulating surfaces. Investigations show this pattern is associated with localised pipe-wall perforation and sometimes pipe fracture. It is proposed that corrosion pitting from the outside surface of the pipe perforates the pipe-wall, allowing fresh oxygenated drinking water from inside the pipe to effuse through the orifice. This then causes a high rate of localised general corrosion under the graphitised layer. The resulting thinning of the pipe-wall may then lead to pipe fracture under high water pressure.

Identification of bacterial types in various atmospheric corrosion sites using standard test kits

It is well-known that bacterial activity can contribute significantly to corrosion in marine and buried conditions. Herein, the possibility of bacterial influence on corrosion under atmospheric conditions is investigated, using the commercially available LAB-BART ® system to identify and to some degree quantify the major groups of bacteria present in corrosion products, including the sulphate reducing bacteria (SRB), iron reducing bacteria (IRB), heterotrophic aerobic bacteria (HAB), denitrifying bacteria (DN), acid producing bacteria (APB) and slime producing bacteria (SLYM). This is sufficient for most engineering purposes to assess the likelihood of corrosion being influenced by atmospherically borne bacteria. Bacterial testing was conducted at nine widely different atmospheric test locations. Significant SRB were not identified at any of the locations, IRB were identified in significant populations at all locations including, surprisingly, at the desert location. HAB were identified in small amounts at some locations but in greater concentrations at a turf farm and at an inland dam site. DN were not present at any location except at the desert site. APB was present in significant amounts at all sites and SLYM varied from almost nil at the ocean beach to quite high populations at the turf farm and at the dairy. These results are compared with nutrient deposition at these sites.

Effect of Nutrient-Based Water Pollution on the Corrosion of Mild Steel in Marine Immersion Conditions

Water pollution is often thought to cause accelerated corrosion of steels, particularly in harbors where levels of oxygenation of the waters may be low and where there may be industrial and shipping wastes. Harbors and coastal regions may also be prone to nutrient pollution from sewage or agricultural run-off. Offshore oil fields also are known to provide sources of nutrient pollution. There are some anecdotal observations but there appear to have been no systematic field or laboratory studies. Recent field observations have been reported on the effect of nutrient-based pollution on the corrosion of mild steel corrosion coupons. These are interpreted in terms of the phenomenological model previously described in the literature for the corrosion of mild steel under marine immersion conditions. A selection of field data previously reported in the corrosion literature is then considered and shown to have characteristics not inconsistent with nutrient-based water pollution. The effect of dissolved oxygen concentration is noted also.

SERVICE LOAD DEFLEXIONS IN PLASTIC STRUCTURAL DESIGN.

Keywords MONASH UNIVERSITY LOADS, STRUCTURAL, ELASTIC, PROPORTIONS, ULTIMATE, PROCEDURE, SERVICEABILITY, BENDING, UNITS, DEFLECTION, DESIGN, THEOREMS, BASIC, APPLIED, LIMIT STATE, ERRORS, MOMENTS, INTEGRATION, PLASTIC, SERVICE, LIMIT ANALYSIS, LIMITS, ANALYSIS, STRENGTH, DIRECT, LOWER BOUNDS, ESTIMATING, DIAGRAMS, FORMULAE... Show All

Long-Term Corrosion of Parked and Abandoned Offshore Steel Pipelines

Internal corrosion of steel pipelines before use, or temporarily taken out of use, and ‘parked’ on the seafloor for some time (months), suspended from operation or ‘abandoned’ for extensive period of time continues to be an issue for offshore operators and regulators. This is irrespective of whether the pipes are gas or oil production or water injection pipelines. Severe pitting corrosion, sometimes observed at the 6 o’clock position, conventionally often is assumed the result of microbiologically influenced corrosion (MIC), particularly if coupled with high bacterial concentrations in the rusts. Dosing with biocides is not always effective and increasingly is considered environmentally undesirable. This paper provides a brief overview of the fundamental requirements for long-term corrosion under low oxygen and essentially stagnant environmental conditions. It shows that any severe internal corrosion at the 6 o’clock position has similarities to that sometimes observed for water injection pipelines and likely the result of under-deposit corrosion resulting from the deposition of rusts and other debris. MIC may contribute providing there is availability of necessary nutrients. Generally similar issues apply for the external and interior corrosion of abandoned pipelines. Avenues for further research and development are outlined, including for pipelines proposed to be abandoned.

Monte-carlo methods for structural reliability analyses

Elementary monte-carlo sampling as a technique to artificially replicate an experimental program has been used successfully for relatively simple problems, provided the failure probability to be calculated is relatively large. The present paper reviews the elementary monte-carlo method and describes a little known, but improved approach known as importance sampling (a).

Investigation of severe corrosion of mooring chain in West African waters

Long-Term Corrosion of Mild Steel in Natural and UV-Treated Coastal Seawater

Highly polished coupons (25 by 25 by 1.5 mm) sourced from the same steel sheet were continuously immersion-exposed either to natural coastal seawater or to seawater from the same source subjected to filtration and UV irradiation to eliminate microbiologically influenced corrosion as much as possible. This was continued for 943 days (2.6 years). Dissolved oxygen levels were very similar in both environments. On average the UV-treated seawater was 2°C warmer, but all coupons exposed to it showed less localized corrosion than those exposed to natural seawater. The typical topographical difference was about 60% as measured by surface roughness parameter Sa. Mass losses in UV-treated seawater were about 10% higher than in natural seawater, but after temperature correction were similar to natural seawater for the first year and tended to be lower subsequently. At all exposure periods the rusts in UV-treated seawater were less voluminous than the rusts in natural seawater. Eventually they also contained a higher proportion of magnetite.

Atmospheric Corrosion of Steel on the Australian Pacific Central Coast

Comprehensive data are presented for corrosion losses of mild steel exposed for up to 5 years, all obtained from exposing steel coupons at one specific severe marine exposure site on the Pacific Ocean coast. The test programme considered the effects of duration of exposure, inclination, orientation, height, shielding, and coupon variability, using multiple, nominally identical mild steel coupons, all under a single local climatic regime. Such a controlled, consistent, natural environment permits unique, valid comparison of the various influences, both for short-term and longer-term exposures, unlike previous tests of some parameters conducted in the short term at disparate sites. In contrast to coupons exposed only on one side, boldly exposed double-sided coupons corroded severely within 3 years. The effects on corrosion behaviour between individual coupons exposed at different heights and vertical continuous single strips of steel are described. Also reported are corrosion losses for continuous strips and for a series of coupons oriented in different directions. Observations of variability in corrosion losses for nominally identically exposed steel coupons are reported. The effect on corrosion losses with continued exposure to 5 years is reported and compared with information available in the literature.

Reply to discussion by G. I. N. Rozvany

Pitting Corrosion of Offshore Water Injection Steel Pipelines

No abstract is provided for this article.

Probabilistic Pitting Corrosion Risk Assessment of Welded Offshore Steel Pipelines

No abstract is provided for this article.

Antipsychotic drug waste: A potential corrosion inhibitor for mild steel in the oil and gas industry

In this study, the corrosion inhibition efficiency of thioridazine hydrochloride (TH), an antipsychotic drug, on mild steel (commonly used pipeline material in the oil and gas industry) in 1 M hydrochloric acid (HCl) was evaluated using electrochemical techniques and weight loss method. Electrochemical impedance spectroscopy (EIS) results suggest that TH significantly enhances the polarization resistance (Rp) of mild steel. Similarly, potentiodynamic polarization results showed that the corrosion current density (icorr) of mild steel decreased significantly with addition of TH. To understand the long-term effect of TH, mild steel was tested for 7 days in 100 ppm TH containing electrolyte. EIS results showed that the Rp did not change significantly after 24 h exposure as compared to 2 h exposure; whereas the Rp increased by 28% after 7-day exposure. Weight loss measurements revealed that the inhibition efficiency of TH is remarkably high (98.8%) after 7-day exposure. The adsorption free energy calculation suggests that at the initial stage (1-day) of mild steel exposure, TH was physically adsorbed onto the surface. However, at a later stage (7- day) the binding of TH was chemical, and hence the corrosion protection increased with increase in the exposure period. As compared to the wide range of corrosion inhibitors reported in the literature, TH has shown to be highly effective for mild steel. Thus, it can be suggested that TH drug waste is a potential corrosion inhibitor for mild steel pipelines in the oil and gas industry.