Volume 31, Issue 3-6

Microbiologically influenced corrosion (MIC) is a complex type of environmentally assisted corrosion. Although poorly understood and challenging to ameliorate, it is increasingly appreciated that MIC accelerates failure of metal alloys, including steel pipeline. Historically, this type of material degradation process has been treated from either an electrochemical materials perspective or a microbiological perspective. Here, we review the current understanding of MIC mechanisms for steel – particularly those in sour environments relevant to fossil fuel recovery and processing – and outline the role of the bacterial biofilm in both corrosion processes and mitigation responses.

As medium-strength steels are promising candidates for the hydrogen economy, it is important to understand their interaction with hydrogen. However, there are only a limited number of investigations on the behavior of medium-strength steels in hydrogen. The existing literature indicates that the influences of hydrogen on the tensile properties of medium-strength steels are mainly the following: (i) the steel can be hardened by hydrogen, as demonstrated by an increase in the yield stress or ultimate tensile stress; (ii) some steels can be embrittled by hydrogen, as revealed by lower yield stress or ultimate tensile stress; (iii) in most cases, these steels may experience hydrogen embrittlement (HE), as indicated by a reduction in ductility. The degree of HE mainly depends on the test conditions and the steel. The embrittlement can lead to catastrophic brittle fracture in service. The influence of hydrogen on the fatigue properties of medium-strength steels is dependent on many factors such as the stress ratio, temperature, yield stress of the steel, and test frequency. Generally, the hydrogen influence on fatigue limit is small, whereas hydrogen can accelerate the fatigue crack growth rate, leading to a shorter fatigue life. Inclusions are an important factor influencing the properties of medium-strength steels in the presence of hydrogen. However, it is not possible to predict the influence of hydrogen for any particular steel that has not been experimentally evaluated or to predict service performance. It is not known why similar steels can have different behavior, ranging from good resistance to significant embrittlement. A better understanding of the microstructural characteristics is needed.

Water leaks in distribution system mains and premise plumbing systems have very high costs and public health implications. The possible in situ remediation of leaks while a pipeline is in service could reduce leaking at costs orders of magnitude lower than conventional pipe repair, rehabilitation, or replacement. Experiences of Roman engineers and recent field observations suggest that such processes can occur naturally or may even be engineered to ameliorate leaks, including those caused by metallic corrosion. Three mechanisms of in situ leak remediation (i.e., metallic corrosion, physical clogging, and precipitation) are described in this paper, in an effort to understand the role of physical factors (e.g., temperature, pressure, and leak size) and water chemistry (e.g., pH, alkalinity, corrosion inhibitors, dissolved oxygen, and turbidity) in controlling in situ remediation for both inert (plastic and aged concrete) and chemically reactive (new concrete, copper, and iron) pipe materials. Although there are possible limitations and uncertainties with the phenomenon, including the fraction of pipeline leaks to which it might apply and the durability/longevity of remediation, such approaches may prove useful in economically sustaining some aging drinking water infrastructure assets and reducing future failure rates.

The development and use of blended cement is growing rapidly in the construction industry mainly due to the consideration of energy, environment, and conservation of resources. Blended cements are produced using any of the supplementary cementitious materials such as silica fume (SF), fly ash, and ground granulated blast furnace slag. The use of SF in concrete may improve the strength and durability of concrete by creating a denser cement matrix compared with conventional concrete, thereby enhancing the service life of concrete structures. In this article, the effect of SF in concrete is reviewed from the point of view of durability. It includes carbonation, resistivity, chloride permeability/diffusivity, sulfate resistance, and corrosion resistance.

The variation of AISI 1045 carbon steel corrosion rate in seawater is investigated under the simultaneous effect of marine parameters in both stagnant and turbulent conditions. The combined effect of salinity, velocity, pH, and temperature is studied using two-by-two graphical curves, while each parameter is applied at three levels. The possible influence of simultaneously acting factors on each considering parameter is experimentally studied and explained using theoretical basis. This paper offers an advantage of considering the simultaneous effect of parameters instead of individual ones, which simulate the experimental media close to the real in-site marine environment where all the affecting factors act in a combined manner. The most innovation of this study is two-by-two investigation of combined action of effective parameters on corrosion rate, which is much more comprehensive and detailed compared to previous researches. Every parameter is considered at three ranges and all the possible interactions with other factors are taken into account. It is proven that the effect of considered parameters on the rate of corrosion is the function of other simultaneously acting factors. The role of fluid velocity condition and also the reaction polarization status is found to be pronounced.