Incorporation of Corrosion Effects into the Life-Cycle Analysis of AW-2017A-T4 Aluminium Alloy under Bending Moment

The paper presents the results of fatigue tests of corroded AW-2017A-T4 aluminium alloy samples subjected to an alternating (symmetrical) bending load. Although there are a number of works describing pre-corrosion fatigue in aluminium alloys, relatively few of them concern bending fatigue effects, in some selected alloys only. Here, the AW-2017A-T4 samples were exposed to electrochemical preliminary corrosion by immersion in an electrolyte, a 3.5% solution of NaCl in water. Several variants of series of samples differing in immersion time were tested. Based on the analysis of the results obtained, Basquin’s fatigue characteristics were developed and compared to the characteristics of the material in its nominal state, which allowed for conclusions on the influence of corrosion effects. The characteristic curves show the susceptibility of the test material to corrosive processes, which results in a decrease in fatigue life along with the increase of pre-corrosion time. The samples with longer immersion duration revealed larger surface losses and widespread corrosion pits.

Synthesis, characterisation and preliminary corrosion behaviour assessment of simulant Fukushima nuclear accident fuel debris

ABSTRACTNuclear fuel debris generated at the Fukushima Daiichi nuclear power plant during the loss of coolant accident in 2011, still resides within the reactor units, constantly cooled by water. Until it is retrieved, the fuel debris will corrode, releasing radioactive elements into the coolant water and the ground surrounding the reactors. To predict the corrosion behaviour of these materials, and to establish parameters for experiments with U-containing and real fuel debris, the corrosion of two surrogate fuel debris materials, with a composition of Ce(1-x)ZrxO2 (x = 0.2 and 0.4), was investigated. Materials were synthesised by a wet chemistry route and pellets were sintered at 1700°C in air atmosphere. Due to the slow corrosion kinetics, aggressive conditions were applied, and corrosion experiments were performed in 9 mol.L-1 HNO3 under static conditions. The incorporation of Zr into the structure of Ce reduced the normalised dissolution rate; from (3.75 ± 0.15) × 10-6 g.m-2.d-1 to (4.96 ± 0.28) × 10-6 g.m-2.d-1 for RL(Ce) of Ce0.8Zr0.2O2 and Ce0.6Zr0.4O2, respectively.

Magnesium, aluminum and zinc co-substituted hydroxyapatite: anti-corrosion properties

Purpose The purpose of this study was to investigate the influence of doping ions Mg2+, Zn2+, Al3+ to the structure of hydroxyapatite (HAP; Ca10(PO4)6(OH)2) and subsequently to evaluate their adaptation in structure and their anticorrosive properties. Design/methodology/approach The substituted hydroxyapatite was synthesized by precipitation method that included the addition of Mg2+, Zn2+ and Al3+ containing precursors to partially replace Ca2+ ions in the hydroxyapatite structure. For precipitation synthesis, three ratios of Ca/P = 1; 1.67; 3 and two values of pH = 7 and 12 were selected. Samples 1 (Ca/P = 1; pH = 7), 2 (Ca/P = 1.67; pH = 7), 3 (Ca/P = 3; pH = 7) and 5 (Ca/P = 1.67; pH = 12) were chosen to monitor the influence of doping ions Mg2+, Zn2+ and Al3+ to the structure of hydroxyapatite and its anticorrosive properties. Findings The chosen synthesis conditions are appropriate for the formation of crystalline HAP substituted by elements Mg, Zn and Al. Only for one sample (1-Mg), two different phases (hydroxyapatite and whitlockite) were identified in the phase composition. On the basis of preliminary corrosion tests, pigments were divided into three groups pursuant to their anticorrosion effectivity: pigments with high corrosion-inhibition efficiency; pigments without anticorrosive properties; and pigments that promote corrosion processes. Originality/value In addition, no doping effect can be observed except for the sample 1-Mg, which consists of two phases (hydroxyapatite and whitlockite). Preliminary corrosion tests prove that some samples of HAP have extremely high anticorrosive effectivity as effectivity of the commercial pigments. The accelerated corrosion test showed that HAP samples have insufficient corrosion-inhibition properties for coating applications compared with the commercial pigment.

Comparative Study of Acoustic Emission Characteristics for Intergranular Corrosion of 316L Stainless Steel Parent Material and Weldment

The 316L stainless steel parent material and weldment specimens were made to carry out intergranular corrosion(IGC) test using the method of boiling nitric acid. During the corrosion experiment, the acoustic emission(AE) signals were collected. Through the comparative analysis of corrosion rate and metallographic structure, the results showed that the IGC of parent material and weldment can be divided into the preliminary corrosion stage and the rapid corrosion stage. The AE parameters and spectrum characteristics of the two corrosion stages of the parent material and weldment were analyzed. The results showed that: in preliminary and rapid corrosion stages, the AE signal amplitude and energy of weldment were higher than that of parent material; the spectrum characteristics of weldment was more abundant than that of parent material. Based on the results of the comparative analysis, the AE sources of parent material and weldment IGC and the possibilities of monitoring IGC using AE technique were analyzed.

Approach to Assessment of Corrosion Growth in Pipelines

Two key components of corrosion growth assessment in pipelines are accurate determination of corrosion growth rate and application of corrosion growth to future integrity of a pipeline. PII has developed a corrosion growth assessment tool, Run Comparison (RunCom) software that allows accurate determination of corrosion growth. RunCom compares the raw signals of the same defect present in two inspection runs to report the real active corrosion defects and their growth with less error. Since variations in corrosion growth along the pipeline can be significant, a single value of average or maximum corrosion growth rate does not represent the corrosion condition of the pipeline and could result in a conservative or non-conservative conclusion for future integrity. PII introduces a Decision Tree Analysis method to categorize the corroded regions along the pipeline and calculate the mean corrosion growth rates in these specific areas. Relationships between corrosion growth rate and defect geometry are also identified. The influence of soil, drainage, and topography on corrosion rates is examined to determine representative corrosion growth rates along the pipeline. A systematic approach incorporating statistical analysis with mechanistic understanding of corrosion for preliminary corrosion assessment of pipeline systems is discussed.