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The subsurface area introduced during rolling on the 1100 aluminum alloy series alters its surface properties, which makes it more susceptible to corrosion. A combination of different transmission electron microscopy techniques is employed to observe the orientation of small grain structures and the distribution elements in the subsurface layer. This approach provided valuable insight into the formation mechanism of the layer and the phenomena taking place during rolling.

Galvanized steel is widely used in transportation and industry. However, the corrosion performance of these products is highly affected while exposed to chloride-containing environments. One alternative is Al-rich metal coatings which are known to notably improve the corrosion protection of the steel substrate by the enhanced barrier properties provided by Al. Although hot dip aluminum-based coatings on steel are nowadays used for many applications, little is known about the electrochemical behaviour of these coatings. This work studies the corrosion behaviour of Al-containing metal coated steel. Odd random phase multisine electrochemical impedance spectroscopy (ORP-EIS) is used for monitoring the corrosion evolution under continuous immersion in a NaCl solution. This technique allows a rapid screening of corrosion processes due to the reduced measurement time with respect to conventional single sine techniques. Extra information concerning linearity, stationarity and noise level is also supplied and can be valuable for further data quality evaluation and fitting. Different equivalent electrical circuits are proposed and their validity is discussed, not only based on physical phenomena but also taking the quality of the obtained data and the statistical evaluation of the fittings into account.

Chromate conversion coatings (CCCs) on zinc have been studied using SEM, AES, XPS and scanning Kelvin probe force microscopy (SKPFM), aiming at understanding the protective mechanism of the CCCs. The SEM images show that the size of microcracks increases with the dipping times in chromate bath, and no crack has been observed when the dipping time is shorter than 5 s. The AES depth profiles show that the concentration of chromium decreases with the depth in the chromate layer, and zinc oxide exists mainly at the interface between the chromate layer and the zinc metal substrate for a coating with dipping time 60 s. The photoreduction of Cr(VI) caused by the X-ray radiation in a vacuum chamber has been investigated by sequentially acquiring the XPS spectra for a chromate coating. By limiting the acquisition time within 45 min, the Cr(VI) reduction by the X-ray radiation is less than 17%. For as-chromated samples, the percentage of Cr(VI) varies from 32% to 42% of the total Cr content in the outer layer of chromate coatings with dipping time from 1 to 60 s. After immersion in the 0.01 M NaCl solution for 24 h, the relative amount of chromium decreased due to mainly loss of Cr(VI) species and zinc oxide/hydroxide emerged on the surface. A lower Volta potential of a chromate layer than the bare zinc has been observed using SKPFM in air, which is in agreement with the open circuit potential measured in 0.01 M NaCl solution using a normal reference electrode. This suggests that the chromate in the coating has a cathodic inhibitive effect in the corrosion of zinc.

Organic primer coatings loaded with environmentally harmful Cr(VI) corrosion inhibitive pigments still play an important role in corrosion protection of aluminium alloys for the aerospace industry. A potential “green” alternative coating system has recently been developed, loaded with lithium salt corrosion inhibitors. Under exposure to neutral salt spray, lithium salts leach from the organic coating into coating defects to induce the formation of a corrosion protective layer. In this work the composition and growth of this protective layer is investigated by time-of-flight secondary ion mass spectrometry (ToF-SIMS). ToF-SIMS imaging is successfully applied to monitor the lateral spread of leaching lithium salts in artificial 1-mm-wide scribes. The chemical composition of the protective layer is revealed by comparing the mass spectra of salt spray exposed scribe areas to the mass spectra of pseudoboehmite and aluminium-lithium layered double hydroxide reference samples. The insights obtained in this work have led to a thorough understanding of the formation mechanism of the protective layer and provide local chemical and structural information which can be linked to corrosion protection behavior.

Chemical inhibitors are widely used to protect metallic alloys from corrosion in aqueous environments. This Letter investigates the possible synergistic behavior of a quaternary ammonium carboxylate compound toward the development of a new system taking advantage of the surface activity of a known antimicrobial surfactant molecule, hexadecyl trimethylammonium cation, combined with a known organic corrosion inhibitor, the trans-4-hydroxy-cinnamate anion. Short-term potentiodynamic polarization (PP) studies combined with immersion in aqueous chloride solutions demonstrated the high inhibition efficiency of the combination of ions, and NMR pfg-diffusion measurements revealed micellar formation that was concentration- and pH-dependent. The NMR data suggest that speciation changes occur in the solution that correlate with enhanced corrosion inhibition efficiency at higher pH and at concentrations above the CMC of the compound. This new contribution may provide a rational molecular design toward delivering corrosion inhibitors to a metal surface through controlled speciation in solution.

A quasi in situ method using a specially developed holder is presented to follow electrochemically induced microstructural changes on a nanometre scale using analytical transmission electron microscopy (TEM). By following a specific specimen area after repeated exposure to oxygen bubbled through aqueous HCl of pH=3, de-alloying of a grain-boundary precipitate of ∼200nm was observed by monitoring the changes in the EELS copper L2,3-edge and EFTEM elemental maps. These results, supporting the existing models of de-alloying of copper rich precipitates in aluminium alloys, demonstrate the effectiveness of the quasi in situ specimen holder for analytical TEM studies of corrosion.

The corrosion behaviour of Cr-coated steel with and without uniaxial deformation was investigated by polarization and scanning vibrating electrode technique (SVET). The Cr coating on low carbon steel is in two different thicknesses, 0.01 and 1.06 micrometers. The chromium-coated steel was elongated up to 25% strain. The results show that the Cr-coated steel has larger corrosion resistance than the uncoated steel. The corrosion resistance increases with the thickness of the chromium coating. The SVET results show that pitting does not initiate at all defects at the same time. The pitting process is unstable. After a pit is covered by corrosion product a new anodic site may start to be active. The uniaxial deformation results in more defects in the coatings and decreases the corrosion resistance of the Cr-coated steel in an environment containing chloride.

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Roman glass is studied here by means of optical absorption spectroscopy, in order to provide an objective method to quantitatively evaluate colour. The dat

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In this work amorphous silicon oxynitride films with similar composition (ca. Si0.40N0.45O0.10) were deposited by reactive magnetron sputtering from a pure Si target under different N2–Ar mixtures. Rutherford backscattering (RBS) studies revealed that the coatings presented similar composition but different density. The mechanical properties evaluated by nanoindentation show also a dependence on the deposition conditions that does not correlate with a change in composition. An increase in nitrogen content in the gas phase results in a decrease of hardness and Young's modulus. The microstructural study by high resolution scanning electron microscopy (SEM-FEG) on non-metalized samples allowed the detection of a close porosity in the form of nano-voids (3–15nm in size), particularly in the coatings prepared under pure N2 gas. It has been shown how the presence of the close porosity allows tuning the refraction index of the films in a wide range of values without modifying significantly the chemical, thermal and mechanical stability of the film.