Analysis of Fe3O4 Protective Coatings Thermally Grown on Color Picture TV Tube Structural Steel Components

Abstract

This article concentrates on the analysis of formation of Fe oxides grown on different treated steel and relation of macroscopic properties of oxides with the structure, composition of layers formed in the color picture (CP) TV tube blackening furnace. Samples subjected to the blackening presented shadow mask, frames and inner shields used in the constructing of CP TV tubes. The chemical composition of the working gas was 100 ppm of O2, 1 % of the volume – CO and 2 % of the volume -H2. The CO2 / CO ratio varied from 5.4 in the introduction part of the furnace to 6.3 at the maximum temperature point of the furnace. The H2O/ H2 ratio varied from 0.19 in the vestibule zone of the furnace to 0.38 in the middle part of the furnace. Inside of the heating zone, the mask temperature was 580 ±10 °C and the whole time of exposure of substrates in the maximum heating zone of steel blackening zone was 5 – 7 minutes. It is shown that blacking treatment of the shadow masks, frames and inner shields structural components of CRT made of A51EKE brings to the formation of iron oxide layer composed of magnetite (Fe3O4) and hematite (α-Fe2O3) where phase composition can vary from 1 : 1 to 1 : 1.5 depending on the surface treatment and subsequent thermal exposure.