The aluminium layer spontaneously forms an aluminium oxide passive film, as is characteristic of aluminium. This film imparts its usual high resistance to major environmental factors influencing corrosion behavior in waters and soils. Corrosion due to dissolved oxygen and carbon dioxide and erosion corrosion due to high velocity waters are the common influential factors in a pipe waterside environment. The passive film imparts high resistance to all of these factors.
Any pitting in the aluminium layer will be arrested at the thick alloy layer. At the alloy layer, pits grow in width rather than in depth. The aluminium layer may exhibit abrasion losses in high velocity rainfall run-off carrying bedload but the alloy layer provides enhanced resistance to mild-tomoderate abrasion. The alloy layer also resists erosion corrosion and corrosion by water and soil, thus providing effective long-term protection.
As a consequence of its combined coating properties, Aluminized Steel Type 2 achieves a superior service life over the full range of normal exposure conditions common to drainage pipe environments. Exceptions include severe abrasive conditions and severe corrosive conditions such as exist in seawater, acid minewater and sanitary sewage..
Coating Protection Mechanism of the Steel Substrate: The very slow rate of pit growth observed in field surveys of pipe up to 43 years old is due to the galvanic protection mechanism of Aluminized Steel Type 2. Should pits penetrate into the steel substrate, three combined pit growth-restricting electrochemical factors are activated.
* Low-level (partial) galvanic protection of the pit cavity is provided by corrosion of the surrounding aluminum layer.
* The electrically insulating oxide films on the aluminium and alloy layers hinder the electro chemical action that powers pitting.
* Partial galvanic protection produces adherent corrosion products that plug pit cavities and retard corrosion.
All there electrochemical factors provide effective long-term substrate protection throughout the entire pipe service life.
*Hot-, cold- and sound- insulation cladding.
* Drainage pipes.
* Roofing and siding for buildings.
Aluminized Steel Type 2 for insulation-cladding Specification:Aluminized Steel Type 2 according to ASTM A 463/A 463M - 06 T2M 300:
T2: means coating Type 2 is a commercially pure aluminum M 300: means minimum coating weight of 300 g/m˛ total both sides
Production-method: Hot-dip coating process.
*Hot-, cold- and sound- insulation cladding. * Drainage pipes. * Roofing and siding for buildings.
Advantages: * Mechanical strength of steel in combination with corrosion resistance of Aluminium results in decreased maintenance cost.
* Fire resistance: No “Metal Embrittlement” (contrary to zinc coatings) Steel base metal protects insulation material against fire.
Storage & handling: dry and ventilated, normal procedures for handling and storing of any quality sheet steel.
Avoid standing water for extended periods.
Not recommended in ammonia containing atmosphere.
Average weight per square meter:
0.56 mm = 4.03 kg/m2, 0.70 mm = 5.15 kg/m2, 0.80 mm = 5.98 kg/m2, 0.90 mm = 6.80 kg/m2, 1.00mm = 7.62 kg/ m2, 1.25 mm = 9.66 kg/m2, 1.50mm 11.70 kg/m2
Thickness of insulation cladding:
Outside diameter of insulated piping | Thickness of Aluminized Type 2 in mm.
Up to 200 mm thickness 0.56 mm
Over 200 thickness 0.80 mm
Removable covers thickness 1.00 mm
Sound insulation thickness 1.00, 1.25 and 1.50 mm
Available coil dimensions and weights
0.56, 0.70, 0.80, 0.90, 1.00, 1.25, 1.50 x 1000 mm, in 1000 kgs - and 2000 kgs-coils.
Formability: Can be bended, corrugated, folded and roll formed. Standard Corrugation 1 1/4’ x 1/4’
Recommended bending radius:
Up to 0.80mm = 1 x thickness / 0.80mm - 1.25mm = 2 x thickness
1.25mm – 1.90mm= 3 x thickness / 1.90mm – 2.20mm = 4 x thickness
Fasteners: Aluminium or stainless steel
For stainless steel fastening systems rubber, plastic, or other insulating materials should be used, to prevent electrolytic corrosion