A novel technology for the corrosion protection of iron archaeological artefacts using parylene base removable bilayer

• Published in: Journal of cultural heritage Vol. 42; pp. 28 - 35
• Main Authors: Blahová, Lucie, Horák, Jakub, Přikryl, Radek, Pekárek, Jan, Tkacz, Jakub, Menčík, Přemysl, Krčma, František
• Format: Journal Article
• Language: English
• Published: Elsevier Masson SAS 01.03.2020
• Subjects: Anticorrosion protection; Conservation coating; Metallic artefact; Parylene; Removability; Anticorrosion protection; Metallic artefact; Conservation coating; Parylene; Removability
• ISSN: 1296-2074; 1778-3674
• DOI: 10.1016/j.culher.2019.09.001

•The Laksil/parylene C conservation coating for iron artefacts is developed.•Much better protection compared to conventional conservation coating is achieved.•The appearance of artefacts is not changed in terms of colour.•The coating is entirely removable and thus the conservation process is reversible. Combinations of different acrylic resins and microcrystalline waxes are most often used for conservation and preservation these days. However, their properties are not sufficient and satisfactory in many ways. A novel barrier coating for the conservation of iron archaeological artefacts composed of parylene C polymer and Laksil lacquer is proposed within this article. Parylene C is a commercial name of poly(chloro-p-xylylene) polymer, and it was prepared via modified chemical vapour deposition. Parylene removability was ensured through the xylene soluble interlayer made of Laksil silicone-acrylic lacquer which was applied between a protected iron model substrate and parylene thin film. The corrosion tests in salt spray showed excellent barrier properties of Laksil/parylene bilayer. The surface roughness measured by the profilometry and the surface morphology shown by the SEM displayed the synergic effect between the Laksil and parylene layer which leads to the exceptional barrier and anticorrosion function of Laksil/parylene bilayer. First, the Laksil layer flattened out rough surface of a substrate; second, thereon deposited parylene film became smooth and defect free and acted as a good diffusion barrier. The colouristic measurements proved that the bilayer does not change the appearance of item, in terms of colour. The EDX and TGA confirmed entirely successful removal of bilayer and thus the reversibility of conservation treatment is enabled. The characteristics of Laksil/parylene bilayer were compared with the conventional conservation coating composed of Paraloid B72 acrylic resin and Revax microcrystalline wax prepared by professional conservators. The Laksil/parylene bilayer demonstrated significantly superior properties in this comparison.