Effects of plasma cleaning and conservation treatment on the corrosion layer of corroded steel – XRD evaluation

Abstract

The application of hydrogen plasma on corroded steel and excavated iron artefacts has been studied. Transformations of the corrosion layer due to the plasma effect were investigated by means of X‐ray diffraction analysis. The reduction of iron oxides to the stable iron oxide, magnetite, was observed for all the samples. In the case of excavated objects, the reduction to magnetite did not occur throughout the whole of the bulk of the oxides, as it does (for example) in the case of steel corroded in the laboratory. Nevertheless, excavated objects, in which a metallic core remained, were stabilised against subsequent corrosion. However, objects that are completely oxidised must be treated carefully, because treatment may result in the formation of a brittle outer layer, and there is a risk of disintegration of such items, if treated using the plasma conditioning and restoration procedure.

Mechanical and chemical results in plasma-surface contact a study of sheath parameters

“…In Plasma Laboratory of ''Demokritos'' a program similar to the programs above runs with great success during the last two decades. 7,18 Two plasma reactors with different dimensions operate, 19 on which we have applied our conceptions, which are basically the enforcement of a d.c potential on the metallic object itself, or on a suitable metallic basis for non conductive artifacts; sometimes the external potential is placed so that it floats (floating), and other times it gives electric current with a circuit. A detailed elaboration of potential sheath parameters, after having adapted it to our conditions, and a proper choice of plasma production gases, is the main purpose of the present work; furthermore, by using the XRD diagnostic method on a large number of excavated and artificially pre-corroded metallic objects, we attempt to understand and interpret the experimental data in agreement with theory, by providing the appropriate chemical reactions.…”

Μελέτη Της Πατίνας Αρχαίων Κραμάτων Χαλκού - Καθαρισμός Και Συντήρηση

“…Στα ίδια συμπεράσματα με την Schmidt-Ott, είχε καταλήξει νωρίτερα η ελληνική ερευνητική ομάδα (Kotzamanidi et al 1999(Kotzamanidi et al , 2002 Όμοια επίδραση έχει το περιβάλλον σε επαμφοτερίζοντες ημιαγωγούς ενώσεις, με χαρακτηριστικό παράδειγμα το χημικό γ-Α1 2 0 3 , που με παρουσία έντονου οξειδωτικού περιβάλλοντος ή αντίδρασης δέκτη ηλεκτρονίων, συμπεριφέρεται σαν n-ημιαγωγός, ενώ με παρουσία αναγωγικού περιβάλλοντος ή αντίδρασης δότη συμπεριφέρεται σαν ρ-ημιαγωγός.…”

Conservation methods of iron artifacts recovered from the marine environment

“…Objects that are completely oxidized, the plasma treatment can turn them, dangerously brittle (Kotzamanidi 2002). Plasma atoms are stopped at the surface of the object, so plasma can not penetrate under the surface of the object.…”

“…The removal of the dirt crust of the excavated artifacts was greatly facilitated in the treatment (Graaf 1995). Kotzamanidi and others (2002) explained the effect of plasma cleaning and conservation treatment on the corrosion layer, and the reduction of iron oxides to the stable iron oxide, magnetite, was observed for all the samples (Kotzamanidi et. al., 2002).…”

“…This is because repetitive initial treatments can help the conservator to remove the softened agglomerates (Kotzamanidi 2002). …”