Page 125 - QRedition5.0 062021

Quality Requirements Edition 5.0 European Enamel Association

8.7.5 Valuation of chipping / spalling on enamellings 8.7.6 Valuation of defects as can be caused by deposits of impurities from different
production lines

Definition and cause
Chipping or spalling on enamellings are mechanical destructions caused by cold Definition and cause
deformation, impact or inner stresses being self-caused within the composite material. In almost every manufacturing process of the enamelling shop (Raw manufacturing- Metal
Chipping or spalling on cutting edges is mostly leading back to an imperfect cutting pretreatment - Milling - Application - Drying - Firing) there are characteristical deposits of
operation or to a too heavy application of enamel. On principle the cause of chipping is, impurities. Inclusions in the enamelling arise in dependence of the contaminating process:
as far as possible, to be cleared on the spot. Defects from a defective mill-lining (Fig. 1 and 2) or superficially molten-on deposit:

Scale, deposited in the furnace (Fig. 3)
Consideration and description

The judgement of damage is performed be naked eye. The description has, among other If sulphuric acid is used in a pickling plant sulphates can be transported (e.g. by hangers
things, also to assess the reverse side of the damaged part.
or via air streams) to the firing area. Deposited spots leave characteristical dimples behind

because of a decrease of the surface tension.
Test report
(Fig. 4 and 5)
To be mentioned in the test report:
kind and origin of test piece
place and date of testing
Fig. 1
description of defect, number and extent
Defective mill-iron shaving
complete state of the article
Fig. 2

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