Identification of enameling defects

Identifying the correct type of enamel defect is the first & perhaps most important step when troubleshooting industrial enameling processes.

Analyzing enameling defects with a digital microscoop.
Analyzing enameling defects with digital microscoop

For this purpose we have invested in a digital microscoop and associated software.

Below some images of common enameling defects.

Little copperheads inside water heater
Large copperhead inside water heater

Blisters

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