In the food packaging sector many efforts have been (and are) devoted to the development of new materials in order to reply to an urgent market demand for green and eco-sustainable products. Particularly a lot of attention is currently devoted both to the use of compostable and biobased polymers as innovative and promising alternative to the currently used petrochemical derived polymers, and to the re-use of waste materials coming from agriculture and food industry. In this work, multifunctional eco-sustainable systems, based on poly(lactic acid) (PLA) as biopolymeric matrix, diatomaceous earth as reinforcing filler and spent coffee grounds extract as oxygen scavenger, were produced for the first time, in order to provide a simultaneous improvement of mechanical and gas barrier properties. The influence of the diatomite and the spent coffee grounds extract on the microstructural, mechanical and oxygen barrier properties of the produced films was deeply investigated by means of X-Ray diffraction (XRD), infrared spectroscopy (FT-IR, ATR), scanning electron microscopy (SEM), uniaxial tensile tests, O2 permeabilimetry measurements. An improvement of both mechanical and oxygen barrier properties was recorded for systems characterised by the co-presence of diatomite and coffee grounds extract, suggesting a possible synergic effect of the two additives.

Pipelines have been installed and operated around the globe to transport oil and gas for decades. They are considered to be an effective, economic and safe means of transportation. The major concern in their operation is corrosion. Among the different forms of corrosion, stress corrosion cracking (SCC), which is caused by stresses induced by internal fluid flow or other external forces during the pipeline’s operation, in combined action with the presence of a corrosive medium, can lead to pipeline failure. In this paper, an extensive review of different factors affecting SCC of pipeline steels in various environmental conditions is carried out to understand their impact. Several factors such as temperature, presence of oxidizers (O₂, CO_2, H₂S, etc.), composition and concentration of medium, pH, applied stress, and microstructure of the metal/alloy have been established to affect the SCC of pipeline steels. SCC susceptibility of a steel at a particular temperature strongly depends on the type and composition of the corrosive medium and microstructure. It was observed that pipeline steels with water quenched and quenched and tempered heat treatments, such as those that consist of acicular ferrite or bainitic ferrite grains, are more susceptible to SCC irrespective of solution type and composition. Applied stress, stress concentration and fluctuating stress facilitates SCC initiation and propagation. In general, the mechanisms for crack initiation and propagation in near-neutral solutions are anodic dissolution and hydrogen embrittlement.

To address the challenge of climate change, future energy systems need to have reduced greenhouse gas emissions and increased efficiencies. For solid fuel fired combustion plants, one route towards achieving this is to increase the system’s steam temperatures and pressures. Another route is to co-fire renewable fuels (such as biomass) with coals. Fireside corrosion performance of two candidate superheater/reheater alloys has been characterised at higher heat exchanger surface temperature. Samples of the alloys (a stainless steel, Sanicro 25 and a nickel-based alloy, IN740) were exposed in fireside corrosion tests at 650 °C, 700 °C and 750 °C, in controlled atmosphere furnaces using the ‘deposit recoat’ test method to simulate superheater/reheater exposure for 1000 h. After exposure, the samples were analysed using dimensional metrology to determine the extent and distributions of corrosion damage in terms of surface recession and internal damage. At 650 °C, the stainless steel and nickel-based alloy performed similarly, while at 700 °C and above, the median damage to the steel was at least 3 times greater than for the nickel-based alloy. Optical and electronic microscopy studies were used to study samples’ damage morphologies after exposure. Intergranular damage and pits were found in sample cross sections, while chromium depletion was found in areas with internal damage. For high-temperature applications, the higher cost of the nickel-based alloy could be offset by the longer life they would allow in plant with higher operating temperatures.

Offshore pipelines are subjected to stresses (e.g., from fluid flow, mechanical vibration, and earth movement). These stresses, combined with corrosive environments and in the presence of trace gases (O₂, CO₂), can increase the pipeline’s corrosion rate and potentially lead to cracking. As such, the impact of trace gases such as CO₂ (linked to enhanced oil recovery and carbon capture and sequestration) on corrosion is key to determining whether pipelines are at increased risk. American Petroleum Institute (API) 5L X70 and X100 were exposed as stressed C-rings (80% or 95% of yield strength). The tests were conducted with either N₂ (control) or CO₂ bubbled through 3.5% NaCl, at either 5 °C or 25 °C. Linear polarization resistance was used to assess corrosion rate, while morphology and variation were determined using optical microscopy (generating metal loss distributions) and scanning electron microscopy. The control experiment (N₂) showed that corrosion rates correlated with temperature and stress. In this low O₂ environment, both alloys showed similar trends. Under CO₂ exposure, all samples showed accelerated corrosion rates; furthermore, the morphologies generated were different for the two alloys: undercutting corrosion with discontinuous microcracks (X70) or deep, wide ellipses (X100). Understanding these changes in corrosion response is key when selecting materials for specific operational environments.

To address climate change, power plants need to switch to greener fuels. One possible fuel is biomass; a carbon neutral/low carbon fuel. However biomasses’ chemistries are both different from coal’s and vary depending on their sources, containing unique levels of the trace elements (e.g., Cl and S) capable of altering the degradation of heat-exchangers. As such, an understanding of the effects of these variations on fireside corrosion is needed. Laboratory testing exposed alloys T91 and TP347HFG in a simulated agricultural product combustion environment at 600°C (up to 1000h; 100h cycles). Three different deposits mixtures were investigated (comprised of KCl, K2SO4, Na2SO4, CaSO4 in different percentages) mimicking accelerated corrosion from different biomasses. Corrosion behaviour was found to be dependant on both alloy and deposit chemistries, with the two materials showing different responses. The deposit with lowest KCl showed lowest corrosion damage, while the highest KCl deposit showed more aggressive behaviour.