Page 125 - 20250602 EEA QM Edition 6.0

Quality Requirements Edition 6.0 European Enamel Association

8.7.2 Valuation of burn-off on enamellings As a result of the firing process, high amounts of iron oxide withdraw the opacifying TiO2
from the enamel layer, due to the formation of iron Titanate (needle like crystals). The
Definition and cause covering power in the defect area is reduced - as a black line is formed (optical
impairment). In the reach of burnings, corrosive stressed articles do not have a complete
Burn-offs or burnings are locally limited defects, caused by a too thin applied enamel
protection against corrosion. Therefore, burnings are to be bound by perfect processed
coating. Due to an excessive oxidation of the metal substrate by firing, the enamel
cutting edges and welding seams.
coat could not form a regular stratified structure or it has been destroyed by a super

saturation of metal oxides. Consideration and description
The judgement of the linear extension of burnings is performed by naked eye and, as
Typical burnings occur on cutting edges or in the reach of welding seams. The agreed upon, to be measured out. The dimension of the destroyed surface is to be
thickness of the destroyed enamel layer is not measurable with customary types of expressed in cm .
2
measuring instruments complying to EN ISO 2178. The determination has to be
carried out on cross sections with the help of a light-microscope. On difficult accessible containers, equipped with protecting anodes, a measurement of
the protective current requirement can be an indication for the extent of burnings.
The illustrations (Enlargement 50 : 1 resp. 500 : 1) display the result of a poor cutting
edge with a direct-on white enamelling. Test report

To be mentioned in the test report:
kind and origin of the test piece
place and date of the testing
description of defects, number and extent
location of defects on the enamelled article

Direct-on white enamelling Direct-on white enamelling
on a squeezed-off edge (50 : 1) on a squeezed-off edge (500 : 1)

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