Corrosion classification through deep learning of electrochemical noise time-frequency transient information

This paper for the first time treats the interpretation of electrochemical noise time-frequency spectra as an imageclassification problem. It investigates the application of a convolutional neural network (CNN) for deep learningimage classification of electrochemical noise time-frequency transient information. Representative slices of thesespectra were selected by our transient analysis technique and served as input images for the CNN. Corrosion datafrom two types of pitting corrosion processes serve as test cases: AISI304 and AA2024-T3 immersed in a 0.01MHCl and 0.1M NaCl solution between 0 and 1ks after immersion, respectively. Continuous wavelet transform(CWT) spectra and modulus maxima (MM) are used to train the CNN, either individually or in a combined form.The classification accuracy of the CNN trained with the combined dataset is 0.97 and with the two individualdatasets 0.72 (only CWT spectrum) and 0.84 (only MM). The ability to additionally classify a more progressedform of pitting corrosion of AA2024-T3 between 9 and 10ks after immersion indicates that the proposed methodis sufficiently robust using combined datasets with CWT spectra and MM. The pitting processes can effectively bedetected and classified by the proposed method. The most important contribution of the present work is tointroduce a novel procedure that decreases the classical need for large amounts of raw data for training andvalidation purposes, while still achieving a satisfactory classification robustness. A relatively small number ofindividual signals thereby generates a multitude of input images that still contain all relevant kinetic informationabout the underlying chemo-physical proces

Listening to Corrosion

Using condition monitoring techniques to achieve predictive maintenance is a prominent topic for military systems. Some of the main challenges related to this topic will be introduced, and after that a specific application will be used to demonstrate the successful development of a corrosion monitoring technique. One of the effective ways to cope with corrosion as a failure mechanism is to use dedicated sensors. Preferably, these sensors do not interfere with the prevalent corrosion process, i.e. they ‘listen to corrosion’ as it occurs spontaneously. A potentially interesting monitoring technique is based on electrochemical noise (EN), which is the spontaneous charge transfer generated by the corrosion process. A unique property of this technique is the possibility to identify corrosion processes based on their EN signature. This work describes the analysis of EN signals, based on which corrosion identification can be performed. Metastable pitting of AISI304 stainless steel serves as an example of the analysis procedure. The effectiveness of the procedure is then demonstrated by means of the identification of microbiologically influenced corrosion (MIC), which is generally regarded as one of the most difficult to predict corrosion mechanisms

A novel and cost-effective double-capsule nanocomposite coating based on carbon hollow spheres with self-healing performance for corrosion protection

The ability of a cost-effective self-healing nanocomposite system to restore its protection functionality in case of a coating defect is of pivotal importance to ensure durable performance under demanding corrosive conditions. In this research, a self-healing epoxy coating was fabricated by incorporation of carbon hollow spheres (CHSs) doped separately with epoxy and polyamine as film forming agents. Graphene-based CHSs were synthesized via silica templating method in presence of sucrose as a carbon precursor. After encapsulation of epoxy and polyamine agents in CHSs denoted as Ep-DCSs and Am-DCSs, respectively, 10 wt. % and 5 wt. % of Ep-DCSs and Am-DCSs were introduced in an epoxy matrix. The final nanocomposite coating was applied on the surface of mild steel substrates. A blank epoxy coating was also used as a control sample. The synthesized CHSs were characterized before and after the silica core removal using field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The CHSs loaded with the film forming agents were evaluated using thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. Furthermore, the protective and self-healing properties of the coatings were studied using electrochemical impedance spectroscopy (EIS), scanning vibrating electrode technique (SVET) and salt spray testing. The obtained results showed that the fabricated nanocomposite epoxy coating can heal appropriately the scratches applied on the surface of the coating barricading the accessibility of corrosive species to the metal substrate (Figure 1). Please click Additional Files below to see the full abstract

Filiform corrosion of aluminium alloys: The effect of microstructural variations in the substrate

Aerospace Engineerin

Modified hydrotalcites as chloride scavengers and inhibitor release agents for improved corrosion protection of reinforced concrete

Owing to the unique molecular structure and high ion exchange capacity, hydrotalcites are believed to have a potential to be modified and tailor-made as an active corrosion protective component of reinforced concrete. In this paper, two types of modified hydrotalcites (MHT-pAB and MHT-NO2) were tested both in alkaline solution and mortar for their possibilities as chloride scavengers and inhibitor release agents for application in concrete. The test in alkaline solution showed that ion exchange occurred between free chloride ions in solution and the intercalated inhibitive anions in the MHTs. The results in mortar validated that MHTs could be promising alternatives for preventing chloride-induced corrosion when an appropriate dosage is adopted and applied in a proper way, in particular, either incorporation of a certain amount (MHT-pAB to replace 5% weight of cement) in the bulk mortar or as a coating of the reinforcing steel (MHT-pAB or MHT-NO2 at 20% weight of cement).</p

The effect of two types of modified Mg-Al hydrotalcites on reinforcement corrosion in cement mortar

Two modified Mg-Al hydrotalcites (MHTs), (MHT-pAB and MHT-NO2) were incorporated into mortar (with different w/c ratios) in two different ways: (1) as one of the mixing components in bulk mortar; (2) as part of cement paste coating of the reinforcing steel. Accelerated chloride migration, cyclic wetting-drying and diffusion tests were performed to investigate their effect on reinforcement corrosion. The results indicated that MHTs could be promising alternatives for preventing chloride-induced corrosion when an appropriate dosage is adopted and applied in a proper way, particularly, replacing 5% mass of cement by MHT-pAB in bulk mortar or as a coating of reinforcing steel (MHT-pAB/MHT-NO2 to replace 20% mass of cement). The effect of MHT-pAB on time-to-corrosion initiation (TTC) of reinforcing steel was estimated using the DuraCrete model. It was found that the incorporation of 5% MHT-pAB in bulk mortar led to a more than double TTC relative to reference mortar without MHTs

Lithium salts as leachable corrosion inhibitors and potential replacement for hexavalent chromium in organic coatings for the protection of aluminum alloys

Lithium salts are being investigated as leachable corrosion inhibitor and potential replacement for hexavalent chromium in organic coatings. Model coatings loaded with lithium carbonate or lithium oxalate demonstrated active corrosion inhibition and the formation of a protective layer in a damaged area during neutral salt spray exposure. The present paper provides an abridged overview of the initial studies into this novel inhibitor technology for the active corrosion protection of aluminum alloys. Coating defects were investigated by microscopic techniques before and after exposure to corrosive conditions. Scanning electron microscopy analysis of cross-sections of the coating defect area demonstrated that the protective layer comprises a typical three-layered structure, which included a dense layer near the alloy surface, a porous middle layer, and a flake-shaped out layer. Potentiodynamic polarization measurements obtained with a microcapillary cell positioned in the coating defect area and electrochemical impedance spectroscopy confirmed the corrosion protective properties of these protective layers. The long-term corrosion inhibition of the lithium-based coating technology was tested in industrial coating systems.(OLD) MSE-6(OLD) MSE-

Hybrid sol-gel coatings for reducing wettability and storage degradation of biomass pellets

Long transport distances and extended storage of biomass pellets especially in humid environments provide a suitable setting for enhanced degradation in the form of moisture sorption, cracking and attrition. We developed an optically transparent, low-cost and environmentally friendly coating to reduce moisture sorption and storage degradation of pellets. The developed coating is a hybrid sol–gel, based on tetraethoxysilane (TEOS) and 3-glycidoxypropyl-trimethoxysilane (GPTMS) precursors. We coated two types of untreated and one type of torrefied wood pellets and stored them in a climate chamber during 1 month simulating a ship's hold, at a constant condition of 40 °C and 85% relative humidity. After 1 month of storage, the mean water contact angle increased by a factor of two compared to the uncoated ones. The lower wettability of the sol-gel coated untreated pellets compared to the non-coated torrefied pellets might provide an alternative to torrefaction.</p