Did you know that Metal Spray can significantly reduce maintenance costs on steel infrastructure? The frequency of re-coating applications plays a major role in the total cost. Metal Sprayed coatings can provide a life to first maintenance in excess of 20 years. The choice of material to be sprayed often depends on the environmental conditions expected for the structure. Unlike other methods, Metal Spray can offer 4 variations of anti-corrosion coatings, all of which have their own benefits and are more favourable in particular environments (Zinc, Zinc Aluminium, Aluminium, Aluminium Magnesium). Metal Spray is the ideal surface to receive any top-coating from painting to powder-coating. No solvents or chemicals are used, there is no limit to the size of structure, and the structure can be sprayed on-site, meaning there are no transport or waiting issues.
Burj Al Arab Hotel (Dubai)
The world famous Burj Al Arab Hotel in Dubai is one of the tallest buildings in the world. It is situated on an artificial island approx. 300m off of Jumeirah Beach which is connected to the mainland by a private curving bridge. Its design was based upon a dhow, an Arabian boat with a triangular sail or sails.
Long concrete piles were driven into the sand to secure a foundation. A surface layer of rocks, circled with a concrete honeycomb pattern, protect the foundation from erosion. Though it took three years to reclaim the land from the sea, it took fewer than three years to construct the building.
The hotel employs 9,000 tons of steel and more than 70,000 cubic meters of concrete. The internal atrium is 180m tall. Despite its size it only accommodates 28 double story floors with 202 suites.
The Metal Spraying Process of the Burj Al Arab:
Metallisation client Ant-Corrosion Protective Systems (APS) used Metallisation Arc Spray equipment as an anti-corrosion protection system of the famous hotel in Dubai. When the Burj Al Arab was being built, vital structural components were metal sprayed to protect against corrosion. In total, 10,000m² of steelwork was arc sprayed, over an intermittent six-month period. The items sprayed included the heli-deck framework, roof mounted mast and 6 diagonal support braces, each weighing in excess of 200 tonnes. The surface was first grit blasted to SA 2.5 cleanliness and then sprayed with 150µm of aluminium using Metallisation’s Arc Spray 140 and Arc Spray 700 systems. The Arc Spray 140 system offered excellent flexibility for hard to access areas, due to its long reach and flexible drive system. The Arc Spray 700 system was used to spray large, less complicated areas as quickly as possible, due to its high spray rate. An epoxy sealer and three coat paint system was then applied for aesthetic reasons and finished with a topcoat of 50 microns of polyurethane. The aluminium coating should guarantee a 15 to 20 year protection against corrosion in the harsh, coastal environment in which the Burj Al Arab stands.
Palace of Westminster, London (UK)
The cast iron roof and flag mast of the Palace of Westminster London (UK) (including Big Ben's Clock Tower and Speaker’s House) were coated with Zinc Metal Spray during its restoration period of 1981-94.
Regents Park Mosque, London (UK)
Her Majesty the Queen officially opened London’s Regents Park Mosque in March 1976. The Dome Structure, approximately 20.6 metres diameter and 12 metres high, was manufactured from mild steel lattice sections and cross-bracings by Tubeworkers Ltd. This Dome section has been protected against corrosive attack using the following specification – grit blasted to SA3 standard, metal sprayed with zinc to 100 microns (0.004”) nominal thickness and subsequently sealed using an olive green inhibitive sealer to Zn4/a. The prime intention of this protective system was to extend the period from erection to first maintenance, thus avoiding costly repeated maintenance programs.
Memorial Colonnade (UK)
This Memorial Colonnade to the late Bishop of Salford UK was erected in a quiet garden setting in the Wardley Cemetery, of Walkden, Lancs. The Colonnade was fabricated in mild steel and to protect the steelwork and afford a first class basis for a paint finish the structure was treated by the Metallisation system, which incorporates a passivated sealing process. It is worth noting that this sealing process itself forms a decorative finish but for purely aesthetic purposes two coats of white enamel were applied to the Memorial Colonnade structure.
Bridges
An example of infrastructure where the Metal Spray process is utilised is the anti-corrosive protection of bridges. Bridges are a significant investment and can span roads, railways or rivers, making maintenance of the steel structure costly in both time and money. For this reason, a high performance and proven corrosion protection coating is often required and specified. Bridge steelwork is very large making metal spraying an ideal solution as work can be completed on-site without the need to dismantle structures.
Around the world, thermal sprayed zinc (TSZ), thermal sprayed aluminium (TSA) or thermal spray zinc/aluminium (TSZA) coatings are commonly specified and applied to give a life to first maintenance of the coating in excess of 20 years. The choice of material often depends on the environmental conditions expected for the bridge structure or sometimes local familiarity with a given material.
New Zealand has many bridge applications including the Auckland Harbour Bridge (NZ) (1958) and the Te Rewa Rewa Footbridge (NZ). Other bridges that have been coated include The Forth Road Bridge (UK) (1964), and the Pierre-Laporte Suspension Bridge across the St Lawrence near Quebec, Canada (where from 1977-79 some 165,000m2 was coated after failure of the original paint system over a six year period), Humber Bridge (UK), The Bosphorus Bridge (Turkey), Tsing Ma Bridge (Hong Kong), The Clifton Suspension Bridge (UK).
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Te Rewa Rewa Footbridge (NZ) |
The Forth Road Bridge (UK) |
The Clifton Suspension Bridge (UK) |
For more Metal Spraying applications on Bridges, Click Here.
Electrical Towers - Protection from Harsh Climates
Electrical towers straddle the landscape and in a lot of cases are very remote; this requires the protection from the varying climates that occur during the 4 seasons. Metal sprayed Zinc has been used not only on new towers but also for the repair of corrosion damaged leg repairs in situ.
Turbines
For more in depth Metal Spraying applications on Turbines, Click Here.
Steam and Land-Based Turbines
Steam and land-based turbines also owe their operating efficiency to Metal/Thermal Spray.
The video below shows a HVAF system spraying a WC-Co-Cr coating being applied on-site onto steam turbine blades in order to protect them from droplet erosion.
Almost every component of the gas turbine engine has some type of coating on it to prevent the damage caused by wear and temperature. HVAF and HVOF coatings are used in the hot section of the engine to coat the shroud with high temperature metals that will not damage the edge of the engine’s turbine blades, yet provide the tight clearance necessary for the engine to function properly. HVAF and HVOF coatings are also applied to the rotating sleeves or bearing found in the hot section of the engine. Common coatings used in this application include T-800 and Chromium Carbide Nickel Chrome coatings.
The above video shows a Kermetico HVAF AK7 spraying Tungsten Carbide on a turbine floor.
Wind Turbines
Wind turbine towers are exposed to harsh external environments, particularly those in an offshore location. A corrosion resistant coating of Zinc is applied both manually and also on automated production lines.
The above video shows the zinc Arc spray coating process of wind towers (turbines) from blast, thermal spray zinc, prime and top coat.
Railway Tracks
Railway Tracks can be Metal Sprayed for Anti-Corrosion protection.
Corrosive environments can reduce rail life vastly. Instances have shown that unprotected rails reported lifetimes of less than six months. In general, loss of rail sections can occur due to corrosion, as well as in more localised areas (e.g. around rail fastenings). It is also important to note that foot fatigue failures often occur as a result of foot corrosion. Corrosion pits (often unseen) on the bottom of the rail can initiate fatigue cracks which can then grow undetected, resulting in rail failure 1.
British Steel, the UK-based manufacturer of premium steel products, has launched a revolutionary new rail product, which can withstand the rigours of being laid in some of the most corrosive of environment 2.
1 Extracted from: https://britishsteel.co.uk/what-we-do/rail/zinoco/
2 Extracted from: https://www.industryupdate.com.au/article/british-steel-launches-revolutionary-new-rail-product
For more Metal Spraying on Railway and other Transport related applications, Click Here.
Sewage Purification Plant
Public utilities, such as sewage works, water works, refuse disposal plant etc., are increasingly treated by metal spraying to prolong the safe life of metal structures. One example is the 3.048m (10ft) diameter by 10.668m (35ft) high Silo installed at a sewage purification works.
The protective treatment specified in this instance was grit blast followed by metal spraying with zinc to 100 microns (0.004”) nominal thickness. One coat of etch primer and one coat of zinc chrome primer were then applied and after erection, an undercoat and topcoat pale blue alkyd resin enamel were applied as a decorative finish.
Mild Steel Filter
The above images, provided courtesy of Grade 2 Impact Blast Cleaning, show the flame spraying of Zinc onto a mild steel filter used in the water industry.
Water Treatment Plant
The photograph shows a Fylde Water Board Tower at Barnacre, UK. The tower was grit blasted to BS 4232, and then zinc sprayed to 175 microns (0.007”) followed by one coat of inhibitive sealer to Zn7/a. Fylde Water Board has adopted this Metallisation Protective System as their standard anti-corrosion treatment, as it has proved over many years to be the optimum for efficiency, economy and maintenance free operation.
Water Treatment Vessels
Eleven 12.19m (40ft) vessels, weighing 10,500kg each, together with nearly 300 smaller units, were treated with Metallisation Zn3/a anti-corrosive system for the North West Water Authority UK. This involved shot blasting to BS 4232 followed by metal spraying with zinc, and finally a coating of a passivating sealer. The main reasons for the Water Board adopting this system was its proven anti-corrosive qualities and the ease with which it can be over-coated with conventional paint.
Bottle Pasteurising Plant
Metallisation system ZN6 has been used to provide an anti-corrosive protection on a Guinness Bottle Pasteurising Plant, designed and built in the UK, for commission in West Africa. The plant will treat 15,300 bottles per hour, and the very humid conditions created by the ambient atmosphere plus the steam generated by the pasteurising process produce particularly corrosive conditions. System ZN6 has been applied to the inside of the main-stream heating tank and to all internal surfaces of the plant. The full advantages of positive cathodic protection is given to surfaces being treated will ensure that the Guinness Bottling Plant will have a long and effective service life. ZN6 = 150 microns of Zinc spray.
Pipelines
An early and successful use of Metal Spray in Australia was on the second Warragamba pipeline (3m diameter and 22km long) built between 1964 and 1969. The first had been coated with the same heat-cured zinc silicate invented by Victor Nightingall and first used on the Morgan-Whyalla pipe line. While these have since been repainted several times, this has been due to delamination of the various over-coating systems and the underlying flame-sprayed Zinc TSZ is still sound. These pipelines supply 80% of Sydney’s water supply.
Street Lighting Columns
Lighting columns are grit blasted, then sprayed with Zinc or Aluminium. It is possible to apply thicker coatings at the base where the environment is more corrosive (as a result of a passing vehicle splashing and/or animal fouling). The columns are then usually painted for decorative purposes.
Water Lock Gates
Lock gates in Paris were treated in 1922 with Zinc and found to be in sound condition 40 years later. Other Lock Gates have been treated in various countries across the world. The Emergency Gates on the Panama Canal are also Metal Sprayed.
For more information on Metal Spray equipment or consumables, call us on 07 3823 1004, or email us using our contact form.
