SAMPLE TEMPERATURE DURING CORROSION REMOVAL BY LOW PRESSURE LOW-TEMPERATURE HYDROGEN RF PLASMA *

The plasma chemical reduction of corrosion layers from archaeological metallic objects is developing since the late 70 th . Contemporary, it is used in some museums, but the optimal treatment conditions are not fully known yet. Treated object temperature is one of the most critical points because metallographic changes can be initiated by elevated temperatures and thus the unique historical information can be lost. Temperature increases due to the direct inductive heating in the discharge as well as by the interaction of the surface with plasma active particles. In the case of samples prepared in acidic corrosion environment, the maximal temperature of the samples with the incrustation was lower than of samples without incrustation treated under the same conditions because the incrustation layers decrease the direct interaction of plasma active particles with the corrosion layers. In contrary, in the case of brass samples prepared in the ammonia atmosphere, the incrustation had an opposite effect due to intense heating of the sample during the reaction with oxygen presented in the outer corrosion layers. The maximal sample temperature was directly proportional to the linear size (or the third root of weight) of the treated sample.