Nolifrit Solution for Black Dots on Cover Coat

Black dots(bubbles or pinholes) on cover coat (mostly on white cover coat) is a common fault of enamel coating process. It may happend in many areas like enamel cookware or enamel panels. What’s the main reason of this fault? And how to avoid this? With experience for over 30 years, technical team from Nolifrit is very professional to solve all kinds of problem like this, and we even have successful cases before:

Typical Case:

One of top 10 manufacturers of cookware in the Middle East.


Black dots on white cover coat (for enamel saucer)

Main Causes:

1, The steel substrate is not clean enough.

2, There are too much C, S, P contained in steel substrate.

3, There are impurities mixed in cover coat enamel slurry.

4, Fire temperature is not reasonably controlled, so the ground coat is rare fired.

Nolifrit Solution:

1, Before enameling, the steel plate should be cleaned, without any rust or dust.

2, Choose better steel plate, enamel grade steel is highly recommended.

3, Avoid the pollution of enamel slurry, and take more careful on the use amount of clay and other additives.

4, Reasonably control the temperature of furnace, ground coat should be fully fired.

(Those advises are all based on our customer’s situation, which subject to the actual practice.)


Problem solved after customer take our advices:

                                             Before                                                                                         After

Hunan Noli Enamel Co,. Ltd is the leader manufacturer of porcelain enamel frit and enamel powder in China. Focused on enamel coating for over 30 years.

We can offer very professional technical guidance and product solutions. To solve the problems our customers will likely face in their production. We have successfully solved most of the problem of our customers, which makes us with very good reputation and build up the profound trust with our customers.