Alclad Products

Alclad products are used where perforation of a product cannot be tolerated. These products consist of a core alloy and a more anodic cladding alloy, usually representing 10% or less of the total thickness, which is metallurgically bonded to one or both surfaces of the core alloy. Any corrosion that takes place progresses only to the cladding-core interface, then spreads laterally as a result of the cathodic protection provided by the core of the cladding. 

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Reprinted from reference 27, pp. 111-145 by courtesy of Marcel Dekker, Inc. bCladding for Alclad products... 

Severe IGC is not observed in high purity Al, or Alclad products that do not form second-phase precipitates at grain boundaries [74]. It is also not observed in alloys that form coarse constituents possessing similar electrochemical properties as the matrix. However, small levels of impurities can induce mild IGC. The mechanisms responsible for IGC is high-purity alloys are complex. They range from... 

Another way to simulate alcladding is to apply a coating of an anodic alloy to an aluminum surface by thermal spray techniques, such as flame or plasma spray. These coatings act in the same way as the clad-(fing layer on an alclad product and corrode sacrifi-cially to protect the core alloy (Ref 11,12). Similarly, anodic coatings (zinc, pure aluminum or a more anodic aluminum alloy) can be applied by hot dipping or vapor deposition. 

Torch-brazed alclad 3003 and alclad 3004 show excellent conosion resistance. Furnace or dip brazing, however, causes a certain amount of silicon difiusion from the clad surface, which limits application of these methods with conventional alclad products. A brazing sheet with filler metal on one side and aldad with a special alloy on the other performs well in furnace or (fip brazing. 

Alclad Products. Because corrosion of alclad aluminum spreads in the plane of the sheet, corrosion of alclad parts results in the ddamination of bonded panels (hence, the expression clad is bacT). Figure 11 shows corrosion in adhesive-bonded clad-alloy joints. Because of the problem, alclad sheet is often avoided for honeycomb fiicedieets. 

The most widely used alclad products are sheet and plate, although wire, tube, and other forms are also produced. The most generally accepted method of fabricating alclad sheet and plate consists of hot rolling to pressure weld the cladding slabs to a scalped core ingot In fabricating alclad products, the temperature... 

Brown, R. H. (ed.) 1969. Alclad and Clad Aluminum Alloy Products, Cambridge, MA MIT Press. 

Alclad A composite wrought product made up of an aluminum alloy core that has on one or both surfaces a metallurgically bonded aluminum or aluminum alloy coating that is anodic to the core and thus electrochemically protects the core against corrosion. 

In order to increase the resistance to atmospheric corrosion of 2000 series alloys used in the aerospace industry, in 1927 Dix from Alcoa proposed [27] protecting them by a cladding in 1050, which he called Alclad . In Europe, this product was called Vedal [28]. 

Dix E.H., Alclad, a new corrosion resistant aluminium product. National Advisory Committee for Aeronautics, technical note no. 259, August 1927. 

Keller F., Brown R.H., The heat treatment of 24S and Alclad 24S alloy products. Alcoa, technical paper no. 9, 1943. 

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