Anodized aluminum is well known for its corrosion resistance. It has been used for almost a century in architectural applications. In this application, it is continuously exposed to atmospheric conditions. Consequently, its service-life can be affected by several factors such as specific microclimates, atmospheric corrosion and degradation. In the case of anodized aluminum, the main components of degradation are changes at the aesthetic level such as changes in color and degradation of the properties of the anodic aluminum oxide (AAO) layer. In the case of coating failures, the appearance of corrosion under the anodized coating is common. Degradation of anodized aluminum can also be characterized by loss of thickness of the anodized layer due to exposure to the environment. Depending on the conditions, different rates of thickness loss can be obtained. Additionally, scratches can occur during transport or use of anodized products, leading to the rejection of products or their substitution. In this work, the response of undamaged and lightly damaged anodized aluminum profiles to simulated environmental conditions was assessed by submitting these to accelerated weathering testing, including ultraviolet radiation exposure and particular humidity-temperature conditions based on natural conditions. Additionally, the AAO layer was characterized by scratch testing and optical and scanning electron microscopy.

High pressure die casting (HPDC) is one of the most commonly used technologies for processing of Al-alloys. Die degradation occurs due to different wear mechanisms such as corrosion (soldering), erosion and thermal fatigue. Soldering is a form of corrosion process in which the interaction of cast alloy and tool surface form layers of built-up material that reduce the die performance and castings quality. To mitigate the soldering problems application of nanolayer coatings containing transitional metal nitrides such as CrN, AlN and CrAlN is advised. However, the performance of CrAlN coatings with different chemical composition is still scarce in the literature. Therefore, this study concerned nanolayered CrAlN coating, with three chemical compositions, deposited on plasma nitrided hot-working tool steel. Soldering of the coating to the Al-alloy was evaluated using a detachment test. The contact surfaces were analyzed using a profilometer, focused ion beam (FIB), scanning electron microscopy (SEM) X-ray spectroscopy (XPS). By analyzing the samples' contact surfaces, it was found that soldering and oxidation occurred on the contact surface and through coating defects. These phenomena have manifested as intermetallic compounds, which formed between Al-alloy and the underlying substrate. Samples with higher number of coating defects exhibited a larger amount of soldering. In detachment test, as a result of soldering, a coating layer detached from the substrate together with the casting. This enabled the analysis of the coating back side and the intermetallic compounds that formed through coating defects. These compounds deteriorated the contact surface between the substrate and the coating. This compromised the contact surface of the coating and the substrate material, which lead to coating delamination. It was found that the chemical composition of the coating had a minor influence on soldering than the density of growth defects. The samples with less defects exhibited less soldering. By reducing the number of coating defects, tool life can be extended.

Graphene oxide (GO) is an excellent filler used in composite corrosion resistant coatings, but its effect is reduced by the fact that it easily forms aggregates. In order to improve the dispersion of GO in the silica matrix and hence, the corrosion inhibiting performance of the composite coatings, the GO was modified with 3-aminopropyl triethoxysilane (APTES) and poly(amidoamine) (PAMAM) dendrimer. The surface-modified graphene oxides APTES-GO and PAMAM-GO were then used as fillers in silica coatings prepared on zinc by dip coating, and their performances were compared with those of GO and reduced GO (rGO). The influence of sol aging on the performance of the composite coatings was also investigated. The methods that have been used for the evaluation of the corrosion resistance of the coatings were mainly electrochemical ones (electrochemical impedance spectroscopy) buttressed with morpho-structural characterizations. The results reveal that the surface modified GO sheets in silica matrices exhibit better results than in case of rGO and GO, and further improvements can be made by sol aging.

Biodegradation process especially at the interface of bioabsorbable metals is difficult to track using conventional analysis strategies (e.g. weightloss measurement and ex-situ surface characterizations). However, assisted by advanced spatially resolved localized techniques, the underlying complicated degradation mechanism emerges in sight. The evolution of local pH and O₂ concentration at the interface of biodegrading metals discloses the progression of the degradation products, particularly the precipitation of Ca-P-containing products, which occupy a significant role during metal biodegradation. In this work, a comparative local measurement of pH and O₂ concentration was executed at the interface of Mg, Zn and Fe alloys in Hank’s balanced salt solution (HBSS) at 37 °C under hydrodynamic conditions. The results revealed that the formation of Ca-P-containing products controlled local pH at the metal interface, and prevented the metal substrate from the interaction with oxygen and water. Local pH at the interface of Mg alloys in Ca²⁺-containing HBSS was found low and stable (7.5-8.1), demonstrating a slight alkalization on degrading Mg in the quasi-physiological environment. A strong consumption of oxygen was found on degrading Zn and Fe, indicating a potential oxygen deficit around Zn- and Fe-based implants. These findings provided valuable insights into the degradation mechanism of bioabsorbable metals.

Data mining (DM) is not a well-understood subject. Data mining is perceived as being a mystical, not mathematically rigorous methodology that often produces results without any validation or verification. Some of that is a correct perception. Indeed, few mathematical theorems demonstrate the rigorous validity of Data Mining. We need to interest more mathematicians in this field—a field that was born from Biology and not from Mathematics. Then, why use it if it is not mathematically fully validated? Simply, it is the best strategy we have knowledge and data are sparse, incomplete, or imprecise. We do not use this technique in a well-defined and well-understood problem where models have been proven and validated. Instead, we use DM when those mechanistic/deterministic models fail, knowledge is insufficient, but data is abundant. Data Mining comprises several mathematical techniques. They fulfill different needs: Expert System is a reasoning-based technique that is useful when knowledge is available and rules on a system’s behavior can be derived. One part of an Expert System is a technique now known as Block-Chain (originally as Black-Board). Information is shared securely. A sharing partner can acquire someone else’s information as long they add information to the blackboard. This technique was popularized by the Bitcoin industry and is now being rapidly accepted by Banks. Expert Systems are used mainly when knowledge is available. Additional information can be obtained by forming knowledge trees that are concatenated. Artificial Neural Networks (ANN) are techniques that can be used when only data instead of knowledge is available. The approach "mimics" the brain's "Pattern-Recognition" capabilities. It is mainly used to extract knowledge from data. There are two main types of ANN: Supervised and unsupervised learning. As an example of Supervise d learning are those ANN tools used to discover relationships between the dependent (output) and independent (input) variables. The non-supervised ANN are frequently used as excellent tools for Data Compression and for estimating the most probable values in incomplete data. Those main techniques get help from Fuzzy Logic, which enables us to deal with the data's uncertainties or with incomplete knowledge that is available. Search Techniques, such as Genetic algorithms (an exciting and fun option instead of Optimization techniques). Traditional Optimization techniques and Statistics are commonly used too as part of Data Mining. In this paper, I will address each technique's fundamentals, discuss the validity of the results, and guide the reader at the best choices for a given problem type. We will close the paper with examples on using the techniques for alloy design and stress corrosion cracking in Nuclear reactors, time permitting.

The corrosion behavior of additively manufactured stainless steel (SS) parts is reliant on metallurgical aspects given by the process, such as microstructural characteristics, residual stress, porosity level, and surface roughness. In the Laser Metal Deposition (LMD), these aspects can be controlled by several process parameters including, laser power, scanning speed, overlap ratio, build direction, powder size, and shape. The iterative layer-by-layer deposition nature of LMD implies successive cycles of localized heating and rapid solidification in the material, which can promote distinct corrosion behavior on SS alloys when compared to the correspondent conventionally manufactured. In this work, the corrosion behavior of martensitic, austenitic, and duplex SS alloys processed by LMD was investigated in a sodium chloride environment. Potentiodynamic polarization scans were conducted to determine the electrochemical corrosion factors and passivity regimes for the LMD SS alloys. The corrosion performance of the materials was also assessed by salt spray test for periods up to 1000 hours. The results were correlated to morphological investigations of the microstructure and the degraded corrosion defects. This work demonstrates a close link between the corrosion performance of additively manufactured SS alloys and the LMD processing parameters.

Chloride-induced corrosion of carbon steel in reinforced concrete is one of the most important failure mechanisms of reinforced structures. Organic inhibitors from different organic groups were analyzed using cyclic potentiodynamic polarization (CPP) to see their effect on the pitting potential of carbon steel in 0.1 M Cl^– contaminated deaerated simulated concrete pore solution (SCPS). It was found that organic compounds with π– electrons functional groups had better performance. This is attributed to the high density of HOMO energies found between the carbon that is double bonded to oxygen, resulting in high tendency of donating π – electrons to the appropriate vacant p or d–orbitals of the carbon steel, resulting in a chemisorption process. It was found that the best corrosion inhibition performance was achieved by polycarboxylates followed by alkanol amines and amines. Another approach to shows the significance of this phenomenon was by developing a quantitative structure-property relationship (QSPR) using a Signature molecular descriptor which correlates the occurrences of atomic Signatures in a dataset to a property of interest using a forward stepping multilinear regression. Data from literature was incorporated in the model, showing that [O](=[C]) is the most influential part of all the inhibitors analyzed demonstrating the significance of π– bond electrons in the adsorption process. Finally, the QSPR model predicted the pitting potentials for the inhibitors used with a high correlation coefficient.

The human activity that we know as “science” is based upon two broad philosophies; empiricism and determinism. Empiricism is the philosophy that everything that we can ever know we must have experienced, whereas determinism posits that the future can be predicted form the past upon the basis of the natural laws, which are condensations of all previous scientific experience. Viewed in this light, “science” is clearly the process of conversion from empiricism to determinism. Thus, observations (experiments) are made empirically and the results eventually lead to the formulation of new “natural” laws that then are used to constrain deterministic prediction to what is “physically real”. The impediment to this process is “complexity”, which is measured by the number of degrees of freedom in a system. Complexity can be likened to a fog that limits the field of view and obscures physico-chemical detail. The advancement of science occurs via the lifting of that fog. Thus, complexity is overcome by using more discerning tools and sensors. Perhaps the greatest tool in lifting the shroud of complexity has been the development of the high-speed, digital computers that are now capable of performing billions of individual calculations per second. Computers have been responsible for the creation of more scientific knowledge over the past several decades than had been created in all preceding human history. Consider the problem of describing the behavior of a cluster of atoms, which in physics is commonly referred to as a “many bodied problem”. The Hamiltonian, which describes the motion of each atom in the system, for a system of 100 atoms was an insurmountable challenge just a few decades ago; now, using supercomputers, clusters of tens of thousands of atoms can be accurately described. Another useful concept in combatting the debilitating effect of complexity is the average property approximation. Consider the problem of describing the propagation of a crack in a piece of iron. For convenience, let us assume that the mass of the metal is 55.5 g. This piece of metal contains 6.023x10²³ atoms and formulation of the Hamiltonian to describe the motion of all atoms in the system, including those atoms at the tip of the crack that are responsible for crack advance, is clearly an impossible task, even with today’s most powerful super computers. However, crack advance is due only to the motion of a relatively few atoms in the vicinity of the crack tip. The remainder of the piece of iron, whose atoms are not involved in the crack advance process, may be assigned “average” properties, thereby greatly decreasing the complexity of the system. It is this approximation that enables deterministic description of physico-chemical phenomena in practical systems (e.g., crack propagation in nuclear power plant coolant piping). An example of the deterministic prediction of damage due to stress corrosion cracking (SCC) in nuclear reactor piping is given by the authors prediction of the depth of a crack in Type 304 stainless steel in the core shroud of a Boiling Water (Nuclear) Reactor as a function of various operating protocols as might be chosen by the reactor operator. Thus, “normal water chemistry” is the standard operating protocol for a BWR in which no attempt is made to modify the redox properties of the coolant (water at 288 ^oC) so as to reduce the driving force of the crack, which is the corrosion potential of the steel. Under this protocol the crack is predicted to grow by about 2.2 cm over the operating period of ten years. The addition of hydrogen to the coolant water in the Hydrogen Water Chemistry (HWC) operating protocol that results in a reduction in the driving force for crack propagation and hence in the crack propagation rate, was originally developed in Sweden as a means of combatting SCC in the coolant circuits of BWRs. If HWC is implemented at the start of operation, the increase in crack length is reduced to 0.6 cm, which is substantial with significant financial implications for the operator and consumer alike. On the other hand, if HWC is implemented after five years, the crack is predicted to grow by 1.9 cm, which is only moderately better than if HWC had never been implemented at all. The reader will note that this “law of decreasing returns” situation is due to the shape of the crack length vs time correlation, corresponding to a decrease in the crack growth rate as the crack grows. This important feature was predicted by deterministic modelling and has since been verified experimentally. The reader will also note that the crack length vs time curves are not smooth. The discontinuities are not due to calculational error but reflect various outages of the reactor, including refuelling outages. From the above, the reactor operator might conclude that, if HWC is to be implemented, then it should be put into effect as soon as possible, if the maximum benefit is to be realized. This example illustrates the benefits of deterministically modelling corrosion phenomena in “real world” scenarios.

Concrete is a strong and hard material used for construction but it can undergo corrosion as a result of water permeation inside the concrete structures. As together with water many aggressive substances get inside the concrete structures, the surface absorbability of concrete is an important factor determining the stability of concrete constructions [1, 2]. One of the effective methods of concrete protection from the adverse effects of water is covering its surface with a protecting coat restricting the permeation of aggressive agents.

The silicon-based compounds, such as silanes, siloxanes and silicones have been often applied in building industry [3]. Organofunctional alkoxysilanes are monomeric silicon compounds that as a result of hydrolysis and condensation produce a stable polysiloxane coating that covers the pore surface. The coating restricts the water permeation but permits free permeation of vapor towards outside of a given concrete element [4]. Another approach applied in order to restrict the adverse effect of water on concrete is the addition of hydrophobic admixtures at the stage of its production [5]. The hydrophobic agents such as fatty acids, their salts (soap), vegetable oils, wax emulsions and animal fats, change the surface tension in pores and cracks, which limits water permeation [5-7].

Our earlier papers present the synthesis of alkoxysilyl derivative based on rapeseed oil (RPTMS) by the reaction of nucleophilic substitution of 3-chloropropyltrimethoxysilane with appropriate sodium salts (rapeseed soap) [8]. The obtained silane has been used for production of wood [8] and steel [9] surface coating protecting from the adverse effect of water.

In this paper we report on an alternative method of synthesis of the above-mentioned silane (RPTMS) from the commercially available oleic acid (OPTES) and propose its use for making concrete surface coating protecting from water permeation inside its structure.

References

[1] Song, H.; Lee, C.; Ann, K.Y. (2008) Factors influencing chloride transport in concrete structures exposed to marine environments. Cement Concr. Compos. 30, 113–121.

[2] Basheer, P.; Basheer, L.; Cleland, D.J.; Long, A.E. (1997) Surface treatments for concrete: assessment methods and reported performance. Constr. Build. Mater. 11 [7], 413–429.

[3] Doran, D.; Cather, B. (2013)Construction Materials Reference Book, Taylor & Francis, (2013).

[4] Carter, P.D. (1994) Evaluation of dampproofing performance and effective penetration depth of silane sealers in concrete. ACI Spec. Publ. 151, 95–117.

[5] Wong, H.S.; Barakat, R.; Alhilali, A.; Saleh, M.; Cheeseman, C.R. (2015) Hydrophobic concrete using waste paper sludge ash. Cem. Concr. Res. 70, 9–20.

[6] Lagazzo, A.; Vinci, S.; Cattaneo, C.; Botter, R. (2016) Effect of fatty acid soap on microstructure of lime-cement mortar. Constr. Build. Mater. 116, 384–390.

[7] Nunes, C.; Slízkova, Z. (2014) Hydrophobic lime based mortars with linseed oil: characterization and durability assessment. Cem. Concr. Res. 61–62, 28–39.

[8] Szubert, K. (2018) Synthesis of organofunctional silane from rapeseed oil and its application as a coating material. Cellulose 25, 6269–6278.

[9] Szubert, K.; Wojciechowski, J.; Majchrzycki, Ł.; Jurczak, W.; Lota, G.; Maciejewski, H. (2020) The Rapeseed Oil Based Organofunctional Silane for Stainless Steel Protective Coatings. Materials 13(10), 2212.

Metal fatigue management is generally well understood as reflected in Aircraft Structural Integrity Management Plans, which in some cases consider environmental degradation prevention, however limited provision beyond find and fix exists for corrosion repair. Thus, the repair of corrosion can be a major through life cost driver and an aircraft availability degrader. This find and fix approach exists largely because tools are too immature to accurately assess the structural significance of corrosion when it is detected. This presentation shows that fatigue and corrosion are decoupled for aircraft in general. Corrosion occurs on the ground whilst fatigue cycling occurs at altitude. This work then aims to provide a crack growth basis for the justification of allowing detected pitting corrosion to remain in service for a limited period.