Dr Robert Petersen

Long-term corrosion loss data for a variety of metals, including ferrous metals, buried in soils were reported in Romanoff (1957) and have often been quoted in the literature. There have been few investigations of the long-term trending of the data. Herein it is shown that the corrosion behaviour of ferrous metals buried in the ground follows a bi-modal trend with time. This trend is observed for a variety of ferrous metals in many different natural environments. Similar trends have been reported also for other exposure environments. Importantly, it indicates that the corrosion process changes over time. This is illustrated for corrosion mass loss and corrosion penetration for a variety of data sets drawn from Romanoff (1957).

The corrosion of old buried cast iron water mains is a problem for the Australian Water Industry. To better manage their assets the industry requires a way of predicting the remaining service life of their pipes. In order to do this a predictive model of long-term corrosion loss with time is required. This paper describes ongoing work being conducted at The University of Newcastle to develop corrosion loss models for cast iron pipes in soils, as a function of exposure time and soil environment. A preliminary corrosion model was calibrated in a previous work, using a limited set of data collected from recent field work. This data base was extended in the current work by including data (of maximum pit depth and some soil properties) from historical condition assessments within the Hunter Water network. Previous studies by the authors (and others) indicate the significance of soil moisture content on the long-term corrosion loss and rate. At most sites soil moisture was only measured at a single point in time (or not at all), so the long-term average value of soil moisture (required for model calibration) was uncertain. To better estimate the average long-term soil moisture content, a simple climate-soil moisture model was developed. This paper presents the collected field data, describes the method for estimating long-term moisture content and presents the updated model calibration based on the additional data.

An electrode array probe, with a novel approach, has been specifically designed to enable the in-situ field monitoring of multiple forms of localised corrosion of steel exposed to marine environments. The initiation and propagation of localised corrosion within the crevice area as well as at the steel weldment were visualised and evaluated over one-year field exposure at two different marine locations in Australia. The results show the varied initiation and propagation behaviour of crevice corrosion and weldment corrosion on steel, which provide experimental evidence for 'bi-modal' behaviour and the change-over of corrosion modes in extended periods of marine exposure.

Corrosion loss data from the 1957 NBS study for steels buried in a large variety of soils and exposed over 12¿17 years are re-interpreted, supported with estimates for scatter in the data. This shows that losses predominantly are consistent with the bi-modal trending pattern also previously observed for steel exposed in a variety of other environments. For short-term and low time of wetness exposures the trends are consistent with mode 1 of the bi-modal trend. These reinterpretations should permit development of better understanding of the factors important for short- and-long term corrosion trends and for improved modelling and prediction.

An experimental study was conducted to assess the effectiveness of strengthening unreinforced-masonry (URM) shear panels with near surface-mounted (NSM) fiber-reinforced polymer (FRP) strips. A total of 23 wall panels (5 URM and 18 reinforced) were subjected to vertical precompression combined with either monotonic or increasing reversing cycles of in-plane lateral displacement under fixed-fixed boundary conditions. Two wall aspect ratios (height/length) and six different reinforcement schemes were tested. The experimental program was designed to produce diagonal cracking in the URM specimens and hence investigate the effectiveness of the various reinforcement schemes in controlling this failure mode. This was achieved for the aspect ratio 1 wall panels. The study revealed that the FRP strengthening was effective in improving the ultimate load, displacement capacity, ductility, and energy dissipation compared with the URM response. For the aspect ratio 0.5 panels, base sliding failures dominated the experimental program, making it difficult to fully assess the effectiveness of the various reinforcing schemes.