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Deterioration of materials
Published in A. M. Sowden, The Maintenance of Brick and Stone Masonry Structures, 2020
Dirt may often become trapped within these calcium sulphate deposits. The easiest method of freeing the dirt and removing the patina is again a water spray, followed by cleaning with light brushing or high pressure water jets, possibly with the introduction of polymer or grit to the latter to increase the abrasive or cutting action.
Ferrous and non-ferrous metals
Published in Arthur Lyons, Materials for Architects and Builders, 2019
Bright zinc tarnishes in the air with the production of a thin oxide film, which is rapidly converted into basic zinc carbonate by the action of water and carbon dioxide. The patina then prevents further degradation of the surface. Ordinary zinc has a lighter blue-grey patina than the alloyed sheet, so the two materials should not be mixed within the same construction. The factory-produced patina is grey or black, but mineral pigments rolled into the surface and coated with a protective film produce subtle red, blue, green or brown pre-weathered finishes. The lifetime of zinc depends directly on the thickness. A 0.8 mm roof should last for 40 years in urban conditions, whereas the same sheet as cladding, washed clean by rain, could last for 60 years. The titanium alloy with considerably improved durability has a predicted life of up to 100 years in a rural environment depending on the pitch of the application.
Sealant Applications
Published in Jerome M. Klosowski, Sealants in Construction, 2017
Copper often has a heavy oxide film (patina), which can be removed chemically but most often for simple sealing is removed by sanding or abrading with steel wool. Solvent cleaning is generally required, even if the surface is abraded. Some sealants, such as acid-curing silicones, are not to be used with copper; others, such as some neutral silicones, give unprimed adhesion. Consult the supplier to determine if the chosen sealant is compatible and if a primer is needed.
EUROCORR 2020: ‘closing the gap between industry and academia in corrosion science and prediction’: part 4
Published in Corrosion Engineering, Science and Technology, 2021
K. Van Den Bergh (ArcelorMittal Global, Gent, Belgium) addressed the subject of, ‘Accelerated corrosion testing of saline resistant weathering steel’. The development of a cost-effective corrosion-resistant steel substrate (without the need for coating), for large off-shore structures would be a great benefit. Weathering steels are mild, (C < 0.2 w/o) low-alloy steels (<3–5 w/o of Cu, Cr, Ni, P Si and Mn) whose enhanced corrosion-resistance is attributed to the formation of a dense, adherent corrosion product layer or ‘patina’. Advanced surface analytical methods were used to provide an in-depth characterisation of the patinas formed after accelerated testing in an environment which simulated severe, saline, off-shore conditions. Weathering steel was also shown in accelerated test (CCT SAE J2334M) to reduce both the general corrosion rate and the delamination rate of coatings. Overall this work has taken forward the development of a cost-effective corrosion resistant steel substrate.
EUROCORR 2020: ‘Closing the gap between industry and academia in corrosion science and prediction’ Part 2
Published in Corrosion Engineering, Science and Technology, 2021
D. J. Mills, D. Nuttall, L. Atkin
D. Mikić (University of Zagreb, Croatia) gave a poster on ‘Electrochemical and spectroscopic study of bronze sculptures exposed to urban environment’. Statues from the 1950s were examined: Nedovršena Igra (NI) from a city-centre and Savskin Žrtvama (SZ) near an oil refinery and busy road. Electrochemical Impedance Spectroscopy (EIS) measurements were made at several points on each sculpture. An electrolyte comprising 2.5 w/o agar in synthetic rainwater (NaCl + Na2SO4 + NaHCO3, all 0.2 g L−1 and adjusted to pH 6.5) was used. Patina composition was determined by Raman Spectroscopy, bronze compositions by XRF. Results showed that ‘NI’ comprised a high-lead bronze, the highest corrosion resistance being found underneath a bluish corrosion product, probably carbonates. ‘SZ’ showed a low Sn but higher Zn content, indicating that it was brass. The impedance readings were lower for NI than SZ. At one location, atacamite was found, probably a result of de-icing salt from the nearby road.
Metallic coloration with Cu/CuO coating on polypropylene nonwoven fabric via a physical vapor deposition method and its multifunctional properties
Published in The Journal of The Textile Institute, 2021
Mei-Lin Huang, Sheng-Guo Lu, Jun-Jian Zhou, Bao-Shan Luo, Yong-Hong Li
In textile dyeing, the K/S value is used to characterize the textile’s dyeing depth, in which the K/S value has a linear relationship with the luster of the fabric. A larger K/S value implies a greater color depth, which represents a higher concentration of colored substances. The appearance colors, K/S value, color difference, and film thickness of the samples are shown in Figure 3. The pristine uncoated fabric was grey, the copper film-coated fabric (zero oxygen flow rate) was orange, and the copper oxide film-coated fabric was dark red and dark green. Copper oxide film-coated fabrics exhibited lighter and brighter colors with the increase of the oxygen flow rate and decrease of the K/S value. The change of color may be due to the changes in the element composition and contents of the film. A patina green color was observed on the surface of copper oxide film-coated fabric at an oxygen flow rate of 10 mL/min, which was most likely caused by the exposure of the sample in a humid air environment. The copper oxide film’s thickness, which is shown in Figure 3(b), gradually decreased with an increase in the oxygen flow rate. Similar results were also observed in the previous research (Ali et al., 2016).