Identifying the correct type of enamel defect is the first & perhaps most important step when troubleshooting industrial enameling processes.
For this purpose we have invested in a digital microscoop and associated software.
Below some images of common enameling defects.
Blisters is a common enamel defect, which is characterized by appearance of circular holes & bubbles in a cooled enameled surface.
May occur as a group, cluster or line of blisters.
Blisters are typically caused by gas evolution during firing, as a consequence of :
- Poor steel quality
- Scratches or damage on base steel
- Large welding seams
- Insufficient cleaning
- Over pickling
- Over blasting
- Impurities in enamel
- Too thick enamel film
- Too high viscous frits
- Contamination of furnace atmosphere
- Under firing
Fishscaling is an enameling defect, which is characterized by small enamel particles chipping off.
Chipping off may happen directly after firing when cooling down or sometimes even days later.
Effected products may usually not be repaired. Due to this reason, this defect is still one of the most described topics within the international enameling industry.
Continue reading “Fishscaling of porcelain/vitreous enamel coatings”
The Italian National Unification institute has published UNI 11734 as of December 6, 2018.
This standard specifies a method for measuring the hydrogen diffusion coefficient in order to determine the fish-scale susceptibility of steels, which can be used in the enamelling process. Continue reading “UNI 11734 : Determining fish-scale susceptibility of enameling steel”
With ultrasonic thickness measurement, you may detect the thickness of individual layers within a multi layer coating.
This may be of great help, when troubleshooting e.g. a two coats / one fire vitreous enameling process.
See our webshop for more details about this and other film thickness gauges.