Porcelain Enamel Coating

From world-class raw materials and production facilities to global presence and process knowledge, we develop product solutions for your porcelain enamel coating and frit needs. Through technical know-how, we formulate specialty frit based products that meet the needs of the consumer white goods, hot water tanks, sanitary ware, cookware, and other industries. We have dedicated R&D centers and staff specialists to assist customers in achieving consistent, high quality output and increasing productivity. As an industry leader, we specialize in understanding the role of porcelain enamel coating and glass enamels across a wide spectrum of applications.

Frits are the basis and main component of an porcelain enamel coating. Each PEMCO® frit is individually designed to address the complex variables of chemistry and end use application. Quality raw materials are blended and melted to create a frit technically adapted for different applications. Our range of products is composed of ground coat, transparent, opaque and white frits that are engineered to match desired color, aspect, or effect.

We engineer PEMCO® frits into a pre-milled, ready-to-use formulation to provide customers with a powder for liquid application. The use of pre-milled products eliminates the need for costly milling equipment. Just add water and mix! One of the most successful innovations in the porcelain enamel coating industry has been the development and continued improvement of our portfolio of PEMCO® Electrostatic Powders. The advantages of electrostatic powders include automated application, elimination of hazardous waste, reduction of energy costs for milling and drying and labor costs in mill room and set up, excellent finish quality, and maximized utilization of material.

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Nolifrit Anti Fishscale frit for Enamel Coating

The fishscale defect in the enamel coating on steel products is well known as an undesired phenomenon. The fishscale defect is caused by hydrogen gas pressure at the enamel-steel interface that causes the enamel to fracture. This problem limits enamellers to low carbon steel in order to avoid fishscale defects. The customers of frit producers often send many different types if steel and ask “is it possible to enamel such type of steel?” This demand has become critical as the hot water tank industry has grown. Consequently, this fact has required a solution for high carbon steel to be found.

Fishscale is a well-known defect in the porcelain enamel industry. Enamellers strictly control their steel to be defect free so they choose special quality steel. When the steel batch arrives, enamellers take samples from each steel coil and carry out initial tests for fishscale. Even with all these precautions, enamellers still face fishscale sometimes. This is mainly caused by variation with the steel coil. It has been seen that development of fishscale resistant enamel could work at least as an insurance mechanism but also could le t enamellers to use lower quality steels.

Fishscale is mainly caused by hydrogen itself. In practice, hydrogen is everywhere in the enameling operation. The main source of hydrogen is moisture in the air. The H2O penetrates the enamel and separates into oxygen and hydrogen. Oxygen is consumed in the adherence reaction, and atomic hydrogen diffuses inside the steel. Atomic hydrogen is too small to penetrate into the steel. hydrogen re-combine to form H2 gas. When the temperature is raised, the hydrogen solubility of steel also increases. This means that steel can absorb more H2 than its capacity. During cooling, hydrogen gas tends to go out from steel due to decreased solubility hydrogen release causes fishscale defects on the enamel surface. The intensity of fishscalling is directly linked with amount of water in the sys tem as well as the absorption capacity of steel.

In the enameling industry, cold rolled steel Is used with several specifications well known by steel producer. Many steel producer have enamel quality steel in their product line. The main requirement is the production method should be cold rolling and the carbon content of steel should be as low as  possible. Several works have been carried out to overcome fishscale.

The fishscale phenomena is affected by both steel and enamel properties. It has been found that adding nickel addition to the enamel helps decrease fishscale. In the work, different enamel systems have been developed for different applications. The steel has 0.25% carbon content, and the result was proved with side by side application.

The main measures to avoid fishscale on enamel coating:

  1. The choice of steel plate: Enamel steel is always the best choice, then cold rolled steel, hot rolled steel is most likely to have fishscale.
  2. The surface treatment of steel plate: Try not use acid pickling, or use little acid pickling in very short time and use corrosion inhibitor when acid pickling.
  3. For the ground coat: Choose the ground coat with suitable adherence.
  4. For the milling additives: Use quartz, carbonate and quality clay in suitable amount.
  5. For the firing process: Fire in reasonable temperature and time, make sure not to burn.
  6. For the thick steel plate, only accept coating on single face.

Hunan Noli Enamel Co.,Ltd has developed a Anti fishscale porcelain enamel frit 2466 to avoid the fishscale defect. It can be even applied in hot rolled steel and the effect can be acceptable.

Enamel coating mixed with 2466 : (Nolifrit)

20180723063339_80425

Enamel coating with normal enamel frit:

20180723063400_40736

Nolifrit Enamel Frit Exported to Central America

Since the arrival of May, the enamel industry has entered its hot season, and we have received orders for enamel frit from customers in Central America. In recent years, Nolifrit has taken the initiative to develop the international market, actively responding to the “One Belt and One Road” policy, and striving to adapt to the new normal of economic development. The effect of market expansion is gradually emerging. In the past few days, Nolifrit has been working hard to promote production, and all employees have worked hard to ensure the timely delivery. The factory has shown a good situation of both production and sales.QQ图片20190511105942_副本

Coming into the Nolifrit production workshop, one and another converter furnaces is rotating at a constant speed, and the molten enamel frit is then quenched.”This year’s situation is quite well, the current orders has been scheduled to June. In order to catch orders, all of our employees are on duty, and now we are still hiring new employees.” When it comes to the sales situation, the head of the company’s administrative department speaks with proud.QQ图片20190511105954_副本

This batch of enamel frit produced for Central American customers can be delivered on schedule, which is the result of the joint efforts of Nolifrit employees. In order to complete the production tasks with quality and quantity, the company’s leadership is reasonably dispatched and production arranged orderly; the supply department closely tracks and strictly guarantees the timely storage of raw materials; the leaders of the production department are willing to work hard and dedicate. All current production tasks are being carried out orderly. The main products of Nolifrit include nearly 2,000 kinds of enamel ground coat, cover coat, transparent frit, and vitreous enamel powder, inorganic pigment, etc. They are exported to foreign markets, such as Southeast Asia, Middle East, Europe and the United States. The continuous overseas orders fully demonstrates the customer’s acceptance of Nolifrit quality.QQ图片20190511110004_副本

Looking at the container trucks loaded with various enamel frits drive out of factory, the hearts of the Nolifrit people are full of pride. “Let Nolifrit go global” is our unshakable goal. Twenty-three years of history is just like a wave, and now we are developing step by step. We will continue to serve global enamel users with our professional service, excellent work enthusiasm and technical and R&D advantages accumulated for over the past 20 years.

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.

Problem:

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.)

Result:

Problem solved after customer take our advices:20190127012903_62344_副本_副本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.

What is porcelain enamel?

In general terms, vitreous enamel, porcelain enamel, copper enamel and jewelry enamel all refer to the same thing. Enamel is a glassy compound applied to and bonded by heat (fusion) to a metal surface; to a copper surface at 1450 degrees F., and to a glass surface at 1100 degrees F. to 1500 degrees F.

The most common glass is a fusion of silica, soda, lime, and a small amount of borax. Though normally transparent, various amounts of opacity can be produced by adding or growing crystals within the glass structure. A wide range of colors are produced by incorporating certain elements, mostly transition metals.

The physical properties of glass can be controlled to permit bonding to most metals, for example, gold, platinum, silver, copper, steel, cast iron and titanium.

The word ‘Porcelain Enamel’ refers to the glass material as well as to the finished product.

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Nolifrit Brief Analysis on Viscosity of Enamel

Viscosity is a measure of the resistance of a liquid to flow. The greater the viscosity, the smaller the fluidity, and the unit of viscosity is Pa•s.

Enamel frit is similar to glass and has no constant melting point. The solid enamel layer is gradually softened and converted into a melt under the condition of constant heating. Therefore, the viscosity of the enamel is continuously changed, and there is no numerical mutation. This is different from crystals. When the crystal is heated to the melting temperature, its viscosity changes abruptly.

Nolifrit Brief Analysis on Viscosity of Enamel

In the first stage of enamelware firing, enamel powder layer decreases in viscosity with increasing temperature; in the later stage of firing, the enamelware gradually cools and the viscosity increases with decreasing temperature. When the viscosity reaches or exceeds 1012 Pa•s, the molten enamel layer becomes a solid enamel layer.

At a typical firing temperature, the enamel melt has a viscosity of 200 to 400 Pa•s.

The viscosity of the enamel depends mainly on the chemical composition of the enamel. The influence of the composition of the enamel on the viscosity is very complicated. The composition and content of the oxide are different, and the influence on the viscosity of the enamel is different in different temperature ranges.

Enamel frit manufacturer found that the introduction of monovalent alkali metal oxides, B2O3 and fluoride in the enamel can reduce the viscosity of the enamel melt; the introduction of SiO2, Al2O3, CaO, MgO, etc., makes the viscosity of the enamel melt increase. When the content of TiO2 in the formulation does not exceed 8%, the viscosity of the enamel melt is lowered; when the content exceeds 8%, the viscosity of the enamel melt is increased.

Milling additives like quartz, zirconium silicate, feldspar, titanium oxide, tin oxide, clay, etc., can not be completely dissolved in the enamel in short firing time and at lower temperature, so this makes viscosity of enamel melt improved.

The enamel with high viscosity is not conducive to the escape of gas in the enamel layer during firing, which increases the pores and bubbles of the enamel layer, and is not conducive to the flow of the enamel melt during firing, which tends to cause the fineness and gloss of the enamel surface to decrease. For enamel products requiring high-temperature firing, enamel with high viscosity is beneficial to improve the burning resistance and firing range of enamel products.

Ceramic Enamel Frit

20190528Available in a variety of colors to harmonize or contrast with the vision area, the ceramic enamel frit is applied to the surface of the glass. Ceramic enamel frits contain finely ground glass mixed with inorganic pigments to produce a desired color. The coated glass is then heated to about 1,150°F, fusing the frit to the glass surface, which produces a ceramic coating almost as hard and tough as the glass itself. A fired ceramic enamel frit is durable and resists scratching, chipping, peeling, fading and chemical attacks.

Application

Spandrel glass can be installed monolithically, using insulated metal backpans, but is more often found as a component of an insulating glass unit. Reflective spandrel glass units are widely used when a uniform all-glass look is desired for the building exterior. Typical applications include commercial fixed windows, curtain walls, storefronts and wall cladding. Spandrel glass is traditionally an opaque material not intended for use in vision areas.

This article comes from obe edit released

 

The Porcelain Enamel Industry

Porcelain enamel has been around for 4000 years and shows no signs of disappearing any time soon. Although alternative materials like stainless steel, plastics and paints continue to gain market share and have completely taken over some markets, such as dishwashers, the cooking and laundry appliance markets remain strong, and total frit production remains about the same. However, some manufacturers believe a huge revolution in materials technology is needed to ensure the continued success of the industry. Both suppliers and manufacturers are doing their share to help ensure that this revolution takes place.

Porcelain enamel coatings are made from a frit based on low melting temperature (2000 to 2500°F) borosilicate glasses. After the glass raw materials are melted (generally in recuperative furnaces) at rates ranging from 5 to 50 tons per day, rapid quenching is used to shatter the resultant glass into small particles. Further particle size reduction is achieved by grinding. The coating is applied using wet suspension or dry electrostatic powder processes, and is then heated to about 1500°F to produce chemical bonding with the metal substrate.

Pre-milled frits now allow enamelers to custom blend their own enamel formulations without using costly milling equipment. The enameler can blend the exact amount required for the job, eliminating waste. Blends can be made almost “just in time,” eliminating the need for a large wet enamel inventory.

Many frit manufacturers have switched from air/gas to oxygen/gas combustion systems to lower their emissions, and this trend is expected to continue. Smelters have become more automated, and larger capacities are being used as product volumes increase through the increased standardization of frits.

For instance, unique appearance characteristics are under development, including metallic lusters to simulate copper metal or stainless steel appearances. Refinements in frit products are also being made to achieve “easy to clean” oven coatings, as well as infrared reflectivity for faster cooking. In addition, hybrid coatings are being investigated to take advantage of properties provided by both porcelain enamel and organic coatings.

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High-Temperature Porcelain Enamel Coating

To attach a porcelain enamel coating to any substrate by enameling, both substrate and glass must be heated to the fusion temperature of the glass. However, fusion methods have not been successful for the more refractory materials. Because most refractory porcelain enamel coatings are amorphous or crystalline in nature, they have to be applied by relatively novel techniques.

Although most ceramic materials are refractory, some of them can be vaporized in an electric arc or hot vacuum. Thin porcelain enamel coatings of amorphous silica can be applied readily to relatively cool substrates by vaporizing metallic silicon or silicon halides in the presence of small quantities of oxygen. Apparently the transfer is accomplished largely as silicon monoxide, which recombines with oxygen on cooling. The process is used to obtain thin, protective, optically transparent films on lenses, certain electrical components, and metal reflectors.

Other porcelain enamel coatings may be produced by vaporizing one or more components of the coating. In this way porcelain enamel coatings of the respective carbides of silicon, boron, aluminum, and chromium can be deposited on graphite, silicon nitride can be formed on metallic silicon, and silicide coatings can be deposited on metals such as tungsten and molybdenum. These processes are necessarily expensive and are poorly adaptable to large specimens or complex shapes.

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Porcelain enamels and ceramic coatings

Earlier definitions of ceramic materials usually stressed their mineral origin and the need for heat to convert them into useful form. As a consequence, only porcelain enamels and glazes were recognized as ceramic coatings until recently, when the principles of phase relations, bonding mechanisms, and crystal structure were applied to ceramic materials and to coatings made from them. In consequence, ceramic materials can now be most safely defined as solid substances that are neither metallic nor organic in nature, a definition that is somewhat more inclusive than older ones, but more accurately reflects modern scientific usage.

Most ceramics are metal oxides, or mixtures and solutions of such oxides. Certain ceramic materials, however, contain little or no oxygen. As a whole, ceramic materials are harder, more inert, and more brittle than organic or metallic substances. Most ceramic coatings are employed to exploit the first two properties while minimizing the third.

Low-Temperature Coatings

The outstanding resistance to corrosion of certain metals, notably aluminum and chromium, is attributable to the remarkable adherence of their oxide films. Aluminum does not corrode because its oxidation product, unlike that of iron, is a highly protective coating. It was once believed that some mysterious kinship between a metal and its own oxide was needed for this protection, but recent knowledge relating to the structure of metals and metal oxides has enabled metallurgists to develop alloys that form even more stable and adherent films. Methods for thickening or stabilizing these oxide coatings by heat treatment, electrolysis, or chemical reaction are widely accepted.

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