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

Fishscaling of porcelain/vitreous enamel coatings

Fishscaling

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.

example of enamel defect called fishscaling

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”

Troubleshooting enameling defects

Resolving enamel defects during an industrial manufacturing process requires a structured three steps approach.

Step I Identify the right defect.
This may sound silly, but it is sometimes not easy to determine what is the exact defect. Incorrect identification will lead to the wrong causes & remedies.
Step II Evaluate possible causes.
Focus your attention on the most logical ones first.
Step III Implement appropriate remedies.

 

Due to the relative complex nature of enameling processes, it might not be easy to resolve an enamel defect.

Please feel free to contact us, if you require any further information and/or hands-on assistance.