Zircoat Refractory Coatings

ZIRCOAT is zirconia rich, high temperature, erosion / corrosion resistant ceramic water - based refractory coating compound, which is available in two grades; ZIRCOAT-HT and ZIRCOAT-M respectively.

Zircoat is the outcome of the untiring efforts put in by our scientists and technicians, backed by a state-of-the-art R&D laboratory.

Zircoat marks the development of a unique refractory coating compound, which will prove greatly beneficial to the industries where erosion/corrosion is a severe and chronic problem for refractories and kiln steel shells.

Main Characteristics & Advantages Of Zircoat

  • Easy to apply by trowelling, brushing or spraying
  • Good adhesion to metals, refractory bricks, monolithics, castables and ceramic fibre modules, molten metal, graphite /carbon crucibles etc.
  • Good adhesion
  • Easy to mix
  • Resistant to severe attack and sand blasting effect of burning fuel oil
  • Resistant to the influence of steam, acids, alkalies, fumes of sulphur and Vanadium compounds and molten metals.
  • Excellent dry strength
  • Excellent resistance to powdering & Gas tight surface without spalling or cracking.
  • Good chemical resistance
  • Reduction in slag adhesion
  • Odourless and nonhazardous
  • Considerable increase in service life of refractory linings and heating systems
Protection for All Furnaces &
High temperature burning systems
Ideal protection for Metals & Refractories
Oil & Gas Industry Power Plants Furnaces and Crucible Manufacturer Cement Industry Rotary Kiln and Boiler Industry

Zircoat Application Procedures

Zircoat is of great advantage to high & low temperature tunnel & shuttle kilns. It considerably extends service life of kiln cars & kiln combustion areas.

1 to 2mm thick Zircoat coating on the heating area increases its service life by 4-5 folds as compared tothe uncoated ones, and also saves on fuel energy by preventing heat energy losses due to leakage through the lining cracks.

Zircoat should be applied on clean surfaces only. Old refractory surfaces must be thoroughly cleaned with a scraper or wire brush, removing all loose pieces and particles. Any glossy surface should be thoroughly roughened with an abrasive disc. Cracks and holes should be cleaned and then filled with a thick Zircoat paste.

Application Procedure of Zircoat-M & Zircoat -HT

Thoroughly dry mix the Zircoat-HT powder, add clean tap water to it to form a smooth paste of toothpasteconsistency. Add required quantity of water to adjust the consistency of the mix to suit brushing, trowelling or spraying applications

To prepare mortar for repairs or plugging, use less amount of water in the mix. The pot life of the good mix is for around 8-10 hours at room temperature. Therefore consume the mix during this period.

For trowelling, brushing or spraying of furnace walls, hearth, ceiling, bridges etc., Zircoat-HT mortar thickness should be around 3mm. If required, further coats can be repeated at hourly intervals to increase the coating thickness. Zircoat-HT thickness should be thoroughly dried out. Zircoat-HT is also used as a cementing mortar for building and laying of new refractory brick lining for which minimum 7 to 8 days drying period is recommended.

Zircoat-M Refractory Coatings

Zircoat-M is a wonder Zircon rich Refractory Coating Matrix ideal for metals and low temperature refractories.

Zircoat-M is Zircon rich refractory coating compound containing high percentage (63%) Zirconia and is most ideal for ferrous and non ferrous metals and refractories except Aluminum metal. Zircoat-M protects from corrosion erosion, chemical fumes and flue gases escaping from heating chambers and severely affecting metals and refractories and thus reducing their service life.

Main uses of Zircoat-M

Zircoat-M is having good adhesion to adhere ferrous. non ferrous metals and low temperature refractories except Aluminium metal

Protects metals and refractories from destructive heat-escaping from the heating ducts and combustion chambers creating corrosion. erosion and cavitations etc. Attacks of destructive chemicals, gases, fumes, flue gases etc. Zircoat-M enhances the service life of chimneys. ducts high temperature burning systems, combustion chambers, kiln furniture and modules etc. Zircoat-M reduces expensive maintenance and plant shutdown cost considerably.

In metal chimenys:- Zirocat-M has to be applied on inside surface only.

Health & Safety

Zircoat-M is eco-friendly in use, odourless, non hazardous, non toxic, non radio active.

Zircoat-M Physical Properties
Colour Creamish
Density 2.90gm/cc
Wt. per cft. 178.5 lbs / 82 kgs
Bulk Factor 1.79
Cold crushing strength 297.5 kg / cm2
Shrinkage at 1200oC < 0.16%
Thermal shock resistance Excellent
Coefficient of Thermal expansion (25-1000°C) 4.32 x 10-6 °C
Electrical properties Good Insulation
Temperature resistance 1500°C
Zircoat-M Chemical Properties
ZrO2 63.00%
SiO2 28.86%
B2O 3 0.63%
Al2O3 0.85%
TiO2 0.34%
Fe2O3 0.068%
CaO 0.91%
MgO 0.34%
Na 3.00%
Flouride 2.00%

Zircoat-HT

Zircoat-HT with its high concentration of Zirconia, resists harsh chemical attacks at high and low temperatures. Around 3mm thick Zircoat coating can work wonders at ambient to 1800° C temperature.

Zircoat -HT prevents leakage of hot gases from heating chambers, thus maximum heat energy is preserved, wear and tear on the Zircoated surface is minimised and coating lasts longer.

Zircoat-HT has unlimited applications and is used in the following areas where continuous and high temperature heating is found hazardous, specially in the heating chambers constructed with conventional materials.

  • Ceramics / Glass
  • Ferrous & brass and other nonferrous metals except aluminium
  • Chemicals and fertilizers
  • Pulp and paper
  • Natural and other gases
  • Petroleum and hydrocarbon
  • Iron and steel
  • Marine and shipping
  • Cement
  • Sugar
  • Coating of kiln furniture, graphite and carbon crucibles. Zircoat-HT coating will be of great benefit to use in the above areas as well as in domestic boilers, induction furnaces, rotary kilns, chimneys, ducts, etc., where fuel oil, gas or electricity are used for heating purpose.
Zircoat-HT Physical Properties
Colour Creamish
Density 3.28 gm/cc
Wt. per cft. 210 lbs / 95 kgs
Bulk Factor 2.11
Cold crushing strength 350 kg / cm2
Thermal expansion 0-1800°C < 1.0
Shrinkage at 1800°C < 0.25 %
Thermal shock resistance Excellent
Electrical properties Good Insulation
Temperature resistance > 1800°C
Zircoat-HT Chemical Properties
ZrO2 65.20%
SiO2 31.09%
B2O3 0.75%
Al 2 O 3 1.00%
TiO2 0.4%
Fe2O3 0.08%
CaO 1.08%
MgO 0.40%

Iron & Steel Industry

In cast iron and steel industry, apply around 3 to 5mm thick Zircoat between ganister and steel shell of the heating chambers of the cupola and accordingly suitable thickness coating for patching receivers, ladles, funnels, spouts etc., and over refractory bricks in reheat furnaces, soaking pits, open hearth floors, furnace doors, sloping floors etc. Zircoat is used as a lubricant in the preparation of steel ingots for better quality and better finish of steel plates, castings etc. Zircoat acts as a barrier and as an armour coat on the linings of electric are furnace, producing special grade steels.

Chemical
Industry

In many chemical processes, corrosive waste gases and chemicals at high temperature cause havoc to the steel structures, such as ducts, furnace shells etc. Waste gases usually contain oxides of sulphur and vanadium. Even at low temperature, the area of acid-resistant bricks collapses because the cement mortar decays under the attack of sulphuric acid. In such cases, Zircoat coating increases the life of heating systems considerably due to its resistance to acids and waste gases. The service life of kilns, furnaces and heating chambers can be extended multi folds if coated with Zircoat.

Town and Natural Gas Industry

A process called cyclic process, carries out the conversion of waste chemicals from oil refineries to industrial heating gas or town gas. Waste refinery gases and heavy naphtha are heated up for a few minutes in converters, where temperature suddenly rises from 105 to 980°C.

This tremendous temperature bounce occurs every couple of minutes; the thermal shock, thus developed can shatter the refractory linings in no time, which can cause explosion of semiburnt gases under pressure-resulting in heavy losses. 12mm thick Zircoat coating on the steel sections of the reacting areas of gas producing units will considerably increase the service life of chambers.

The coatings can perform satisfactorily and offer prolonged protection. The life of heat transfer units of domestic and industrial boilers can be improved further by applying 3 to 4mm thick Zircoat over the refractory lining.

Pulp and Paper Industry

High consumption of thermal energy is necessary for chemical conversion of wood into paper pulp and subsequent recovery of unreacted chemicals involves reliable refractory structures. Regions of high mechanical abrasion (as in ash flumes, the hoods of lime kilns and boilers in which heavy fuel oils are burned) often sufferfrom rapid erosion.

Severe spalling of refractories can occur when they are subjected to violent and and wet fuel comes in contact with hot furnace walls.

In this and in many chemical industries, problem of normal refractory wear developed from thermal or mechanical stresses is further aggravated by chemical attacks by reactive substances present in or produced by pulping or recovery process. Zircoat-HT refractory coating is exceptionally stable and durable under conditions of thermal, mechanical and chemical onslaught encountered in the pulping process. 3 to 4mm thick Zircoat-HT coating can increase the service life of heating systems by many folds.

Induction Melting Furnaces

Induction furnaces are used for melting ferrous and nonferrous rnetals. During the molten metal melting process, generally following problems are observed:
1. Rammed silica lining cracks due to thermal shocks.
2. Slagging of molten metal passage obstructs free flow of metals.
3. Eroding of silica lining.
4. Faster leaching out of refractory bricks which came in contact with molten metal.
5. Cracking of bricks and escape of molten metals.
6. Molten metals getting contaminated because of leached out constituent from lining bricks.
Zircoat-HT is excellent to protect the heating system from above problems.

Shipping
Industry

In ships, furnaces/boilers producing heat for generation of steam are fired with fuel oil. Because of months of nonstop operation of these furnaces/boilers, refractories get severely damaged due to the hot corrosive gases developed from fuel oil. At elevated temperature, presence of small percentage of sulphur-dioxide, trioxide, vanadium pentoxide etc. damages refractory brick work. 3 to 5mm thick Zircoat applied on the refractory brick lining and also if used as a brick lining mortar, will enhance the life of furnaces/boilers considerably. Zircoat-HT is found as an excellent mortar for laying new refractory brick lining in high and low temperature furnaces and kilns.

Sugar
Industry

In the sugar industry, plant managers will find Zircoat-HT as an ideal cost-saving remedy for speedy repairs and maintenance of combustion chambers in lime kilns, pulp dryers, steam boilers, coal, gas fired and oil-fired furnaces or wherever sugarcane waste is burned as a fuel

Zircoat-HT has proved a reliable, economical and cost-saving remedy in sugar producing mills. As a rule, plant repairs are generally carried out before the peak season starts when sugarcane juice is in abundance

Harvesting of sugarcane keeps the plant working at optimum capacity for four to five months at a time. For the rest of the year the plant remains idle when patching and repairs can be conveniently carried out. In producing sugar from sugarcane, a large amount of sugarcane waste is burned as a fuel. This process produces hazardous chemical gases, which are corrosive at elevated temperatures. These chemical gases damage most refractories and firebricks, causing heavy breakdowns, which lead to great financial losses. Zircoat-HT is found to be the most suitable remedy for speedy repairs of damaged areas.

Carbon/Graphite Crucibles

Crucibles are used for melting of ferrous and non ferrous metals. In metal melting process these crucibles are severely affected by molten metals at elevated temperatures, and it is generally experienced that they fail in just few charges.

Life of these expensive crucibles can be extended considerably by applying 2 to 3mm thick Zircoat-HT coating on the inside and outside walls of crucibles. Since Zircoat-HT is incompatible (unfriendly) with carbon / graphite, following procedure is suggested for coating the crucibles.

Form a brushable Zircoat paste by mixing 5% Sodium Silicate solution in clean tap water. Ensure that crucible walls to be coated are rough and clean enough so that the coating adheres well over them. Apply 2 to 3mm thick Zircoat by brushing and allow the coated areas to dry out for a couple of days in warm atmosphere. The first heating of crucibles should be slower than normal. Around 2mm thick Zircoat-HT coating can double the life of crucibles.

Caution: Improper drying of Zircoat coated-HT crucibles may cause cracking/shattering during first heating.

Kiln
Furniture

Life of silicon carbide, mullite, alumina and cordierite refractory kiln furniture can be increased considerably by brushing or spraying with 1 to 2mm thick Zircoat.

Petroleum and Hydrocarbon Industry

A huge amount of heat is vital for smooth and efficient running of a refinery. 260 to 2000° C temperature is employed continuously to crack down the crude oil and convert it to useful end products. The refinery runs more economically if the heating process is kept uninterrupted. Continuous high temperature corrodes the plant faster. Zircoat-HT is an ideal remedy to protect the plant from corrosion.

Use of Zircoat-HT in Induction Melting Furnace

The refractory brick lining between electric bobbins and silica ramming is the vital part of the induction melting system, and sensitive to thermal shock and physical wear.

Zircoat-HT is used to reinforce these refractory bricks by trowelling with 3 to 4mm thick coating on outside and 5 to 6mm thick coating on inside refractory brick walls. Coating has to be properly dried up to set it hard.

The brick wall is thus reinforced by Zircoat-HT and it becomes super resistant to wear and sudden break downs due to thermal shocks. After repeated usage of Zircoat-HT, service life of furnace can be increased multi folds

After proper setting of Zircoat-HT, silica sand has to be rammed in between the steel sleeve and 5mm thick asbestos or mica sheet to form an average silica wall thickness of 200mm. Melting of steel starts and the steel sleeve is allowed to melt away and get dissolved in the molten steel. After removing the molten metal from the trough, coating of pure silica is formed on top of the Zircoat-HT coating.

Rotary Kilns

Zircoat-HT is also an ideal and excellent refractory coating for rotary kilns, ducts etc. 25mm thick Zircoat-HT coating is sufficient for obtaining superior results. It reduces the gross weight of the rotary kiln and eliminates the risk of thermal shock damages.

Procedure for application of Zircoat to Rotary Kilns :

1. Weld 6mm dia x 57mm L steel studs to the inside tubular kiln chamber wall at (12") 305mm centres.

2. Apply around 25mm thick Zircoat-HT coating (in convenient small thickness layers) on the bottom half of the cylinder and fasten a mild steel wire mesh to the bolts over the coated area and press it tightly. The Zircoat-HT coated shell has to be heated for around 24 hours at temperature 200°C to completely dry out the moisture and set the Zircoat-HT hard.

After thoroughly drying out the Zircoat-HT, again apply a second coat of 25mm thick Zircoat on the surface of wire mesh and repeat a further layer of wire mesh tightly secured over the coated area, once again thoroughly dry up the coated area at 200°C for further period of around 24 hours. This makes total thickness of Zircoat-HT coating around 55mm above the steel shell. Again tightly fix up the wire mesh over the coated area and apply a final coat of around 5 to 6mm to ensure that the steel studs are totally immersed in Zircoat-HT. System should be heated up for around 54 to 60 hours at 200°C and ensure that all the moisture is completely removed. After that the temperature can be increased at the usual rate.

Guidelines To Use Zircoat-HT Efficiently

Precaution: After coating the area with Zircoat-HT the first firing should be carried out slowly to avoid development of any surface cracks or other defects due to the moisture content in the coating material. The applied Zircoat coating should be air dried for minimum 24 hours and then slowly raise the temperature to 600°C at 20 to 25°C / hr and then to operating temperature at around 50°C / hour. For large coating thickness adequate air dying is required to avoid cracks the Zircoat-HT coating

  • 1. The surface to be coated with Zircoat-HT should be cleaned thoroughly.
  • 2. Refractory surface should be cleaned with scraper or wire brush removing all loose pieces, particles etc.
  • 3. Glossy surface should be roughened enough with an abrasive disc.
  • 4. Before applying Zircoat-HT, the surfaces of refractories, castables etc. should be dampened with water.
  • 5. Before mixing water to Zircoat-HT powder, it should be thoroughly dry-mixed. Then water should be added and mixed homogeneously for better adhesion. The pasty mass should be consumed within the stipulated pot life of 8 to 10 hours.
  • 6. Mixing, applying, drying and first firing should be done strictly according to the procedures laid down in the brochure.
  • 7. If coating beyond 2mm is applied, it should be in multiple layers for proper drying.
  • 8. After consuming part quantity, the left out Zircoat-HT dry powder should be kept air tight to avoid absorption of outside moisture. This will ensure longer service life.

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