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 Zirconia Ceramic 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.

MAX SUITABLE TEMPERATURE
Zircoat - M : 1500OC Zircoat - HT : 1800OC
Zircoat Refractory Coatings | Zirconia Ceramic Refractory Coating

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.
  • 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.
  • 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
Protection for All Furnaces &
High temperature burning systems
Oil & Gas Industry Power Plants Furnaces and Crucible Manufacturer Cement Industry Rotary Kiln and Boiler Industry

Applications

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

5mm thick Zircoat coatings offers as good a protection and insulation as a 130mm thick insulation fire brick.

Zircoat 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 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.

  • Ceramic / Glass
  • Aluminium, brass and other nonferrous metals.
  • 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 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.

Application Procedure of Zircoat

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. Before applying Zircoat, the surfaces of refractories, castables etc. may be dampened with water.

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

Excess water will lead to high shrinkage, crack development & loss in mechanical strength.

The pot life of the good mix is for around 8-10 hours at room temperature. Therefore consume the mix during this period.

Application : Coat the surface by brush, spray or troweling to a thickness of 1-3 mm.

If required, further coats can be repeated to increase the coating thickness. Zircoat is also used as a cementing mortar for building and laying of new refractory brick lining.

Drying : Allow each coat to dry thoroughly at ambient temperature. (For 1-3 mm thick coats 24 hour; for thicker coats & mortar masses 24-72 hours).

Initial Firing : Raise temperature slowly at the rate of 20OC - 25OC / hour up to 600OC. Thereafter at usual rate to bonding temperature.

MINIMUM BONDING TEMPERATURE
Zircoat - HT : 1500OC Zircoat - M : 750OC
____

CHEMICAL PROPERTIES

Properties ZIRCOAT - M ZIRCOAT - HT
ZrSiO4 > 85 % > 98 %
Others < 13 % < 2 %

PHYSICAL PROPERTIES

Properties ZIRCOAT - M ZIRCOAT - HT
Colour Creamish Creamish
Coverage
(1mm Thick)
2.5 kg/sqm 2.5 kg/sqm
Bulk Factor 1.79 2.11
Bulk Density (Powder) 1.60 1.90
Bulk Density (Coating) 3.0 g/cc (1000 OC) 3.1 g/cc (1600OC)
Apparent Density 4.1 g/cc (1000 OC) 4.5 g/cc (1600OC)
Porosity 27 % (1000 OC) 32 % (1600OC)
Water Absorption 9 % (1000 OC) 10 % (1600OC)
Shrinkage < 1 % (1000 OC) < 2.5 % (1600OC)
Cold Crushing Strength 297.5 kg/cm2 350 kg/cm2
Electrical Properties Good Insulation Good Insulation
Thermal Shock Resistance Excellent Excellent
Thermal Conductivity
(1000 OC)
0.55 W/mK 0.45 W/mK
Temperature Resistance 1500 OC 1800 OC

Guidelines to use Zircoat efficiently

Precaution : After coating the area with Zircoat 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 OC at 20 to 25 OC and then to operating temperature at around 50 OC / hour.

  • The surface to be coated with Zircoat should be cleaned thoroughly.
  • Refractory surface should be cleaned with scraper or wire brush removing all loose pieces, particles etc.
  • Glossy surface should be roughened enough with an abrasive disc.
  • Before applying Zircoat, the surface of refractories, castables etc. should be dampened with water.
  • Metal surfaces, should be free from any grease, rust of oil, Grease or oil should be cleaned with trichloroethylene and rust with rustoline. The surface should be roughened enough with an abrasive disc or and blasting.
  • Before mixing water to Zircoat 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.
  • Mixing, applying, drying and first firing should be done strictly according to the procedure laid down in the brochure.
  • If coating beyond 2mm is applied, it should be in multiple layers for proper drying.
  • After consuming part quantity, the left out Zircoat dry powder should be kept air tight to avoid absorption of outside moisture. This will ensure longer service life.

THE USE OF ZIRCOAT IN SOME MAJOR INDUSTRIES

Non Ferrous Metal Industry

Zircoat is excellent for use in ferrous and nonferrous metal and other alloy industries.

In aluminium, brass and its alloy industries, alumina refractory bricks which come in contact with molten aluminium or other nonferrous metals get corroded faster because their alumina content gets leached out. Zircoat which contains higher percentage of Zirconia in its residual is incompatible with molten metals. Therefore 3 to 5 mm thick Zircoat coating on the face of refractory brick linings acts as a barrier and an armour to molten metals which arrests leaching of bricks, thus considerably enhancing the life of the heating chambers.

Zircoat-M Refractory Coatings
Zircoat-M Refractory Coatings

Chemical Industry

In many chemical processes, corrosive waste gases and chemicals at high temperature cause havoc to the steel structures, such as chimneys, 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 chimneys, steel shells and ducts can be extended multi folds if coated with Zircoat.

Fertilizer Industry

Generally frequent breakdowns are experienced in high-temperature zones. In chemical processing units 3 to 5 mm thick Zircoat will work as a barrier coat between heat transfer walls and corrosive chemical gases. This prevents costly breakdowns.

Zircoat-M Refractory Coatings
Zircoat-M Refractory Coatings

Rotary Kiln

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

Kiln Furniture

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

Zircoat-M Refractory Coatings
Zircoat-M Refractory Coatings

Iron and Steel Industry

In cast iron and steel industry, apply around 6mm 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 furnace, producing special grade steels.

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 4 mm 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 is found as an excellent mortar for laying new refractory brick lining in high and low temperature furnaces and kilns.

Zircoat-M Refractory Coatings
Zircoat-M Refractory Coatings

Petroleum and Hydrocarbon Industry

A huge amount of heat is vital for smooth and efficient running of a refinery. 260 to 2000 OC 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 is an ideal remedy to protect the plant from corrosion.

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 OC. This tremendous temperature bounce occurs every couple of minutes; the thermal shock, thus developed can shatter the refractory linings in not time, which can cause explosion of semi-burnt gases under pressure resulting in heavy losses. 12mm thick Zircoat coating on the steel sections of the reacting the service life of chambers. The coatings can perform satisfactorily and after prolonged protection. The life of heat transfer units of domestic and industrial boilers can be improved further by applying 3 to 4 mm thick Zircoat over the refractory lining.

Zircoat-M Refractory Coatings
Zircoat-M Refractory Coatings

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 of 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 3 mm thick Zircoat coating on the inside and outside walls of crucibles.

Since Zircoat 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 3 mm 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 that normal. Around 2mm thick Zircoat coating can double the life of crucibles. Caution : Improper drying of Zircoat coated crucibles may cause cracking/shattering during first heating.

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 suffer from rapid erosion. Severs spalling of refractories can occur when they are subjected to violent and frequent thermal shocks, such as in hog fuel boilers where cold 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 refractory coating is exceptionally stable and durable under conditions of thermal, mechanical and chemical onslaught encountered in the pulping process. 3 to 4 mm thick Zircoat coating can increase the service life of heating systems by many folds.

Zircoat-M Refractory Coatings
Zircoat-M Refractory Coatings

Sugar Industry

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

Zircoat 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 keep 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 is found to be the most suitable remedy for speedy repairs of damaged areas.

Induction Melting Furnaces

Induction furnaces are used for melting ferrous and nonferrous metals. During the metal melting process, generally following problems are observed.

  • Rammed silica lining cracks due to thermal shocks.
  • Slagging of molten metal passage obstructs free flow of metals.
  • Eroding of silica lining.
  • Faster leaching out of refractory bricks which come in contact with molten metal.
  • Cracking of bricks and escape of molten metals.
  • Molten metals getting contaminated because of leached out constituents from lining bricks.
  • Zircoat is excellent to protect the heating system from above problems.
Zircoat-M Refractory Coatings

Use of Zircoat-HT in Rotary Kilns

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

Apply around 25mm thick Zircoat 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 coated shell must be heated to completely dry out the moisture.

After thoroughly drying out the coating, again apply 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. This makes total thickness of Zircoat-HT coating around 55mm above the steel shell. Apply a final coat of around 5 to 6mm to ensure that the steel studs are totally immersed in Zircoat. The System should be heated up for around 48 hours until 150 OC to ensure that all the moisture is completely removed. After that the temperature can be increased at the usual rate.

Zircoat Refractory Coatings | Zirconia Ceramic Refractory Coating

Use of Zircoat in Induction Melting Furnace

Zircoat Refractory Coatings | Zirconia Ceramic Refractory Coating

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

After proper setting of Zircoat, 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 200 mm.

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 coating.

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

Mixing of Zircoat for Trowelling Application

Thoroughly dry mix the Zircoat powder, add clean tap water to it form a smooth paste of toothpaste consistency. 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 post 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 mortar thickness should be around 3 mm. If required, further coats can be repeated at hourly intervals to increase the coating thickness. Zircoat coating should be thoroughly dried out.

Zircoat 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 Refractory Coatings | Zirconia Ceramic Refractory Coating

Use of Zircoat in some major industries

Zircoat Refractory Coatings | Zirconia Ceramic Refractory Coating

6 to 12 mm thick Zircoat coating prevents steel sections from the attacks of the hot corrosive gases escaping upwards. The coating procedure is given as under :

Weld 6 mm dia x 25 mm long steel studs to the inside steel chimney wall at around 300 mm centres. Apply 6 mm thick Zircoat on the inside section of the chimneys and fix with a steel chicken wire mesh to the bolts. Heat up the Zircoat coated chimney cylinder at 200 OC temperature for around 20 hours. After heating, apply final coat of 2 to 3 mm thick Zircoat on the laid out wire mesh to level the coated area and to totally cover the wire mesh and steel studs. Dry up the Zircoat coated area thoroughly.

Zircoat effectively acts as a barrier against corrosive gases and absorbs chemical attacks.

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

1 to 2 mm thick Zircoat coating on the heating area increases its service life by 4-5 folds as compared to the 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.

Firing Schedule

Raise the temperature at the rate of 20 to 25 OC per hour upto 600 OC evenly and thereafter the furnace may be further heated up to a final temperature at the usual firing schedule.

2.5 kg Zircoat covers around 1 mm thick 1 sq. meter area.

Shelf Life

One year + in close airtight container.

Packaging

Zircoat is available in strong airtight polythelene lined plastic containers, containing 5, 10, 25 kgs. Also larger quantity (50 kgs and above) packing is available in tropic-proof tough polythelene lined stackable steel drums. Such containers are packed in multiples on strong sea worthy pallet type wooden crates.

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