Alclad aluminum

Aluminum alloy (and in particular alclad aluminum) tubing is sometimes used in water service. The alclad alloy has a sacrificial aluminum-alloy layer metallurgically bonded to a core alloy. 

Panels of 24-ST alclad aluminum, 6x6 inch 0.032 sage, are coated with the fire-retardant system (only one surface) and placed in the vibrating test rig. 

Aged in nitrogen on 17-7 pH stainless steel - a Aged in air on 2024T-3 alclad aluminum o Aged in air on 17-7 pH stainless steel ... 

Aluminum Pipe) A Heavy Wall Alclad Aluminum "Spool Piece" Will Avoid Galvanic Corrosion of Pipe... 

An ideal model system was selected to study the interfacial factors with EIS [19]. The model system was Parylene C-coated Alclad (aluminum-clad aluminum alloy). In this system, the surface state of the top surface (salt solution/coating interface) and the adhesion of the coating (coating/metal interface) were modified to study the influence of these factors on the corrosion protection performance of the system. 

Many of the primers developed during the past 20 years contain corrosion inhibitors. These primers have a second function to further improve hydrolytic stability at the adhesive to metal interface and prevent corrosion during exposure to salt spray. Table 1 shows the difference in strength retention of 2024-T3 alclad aluminum lap shear coupons exposed to salt spray. Both sets of coupons were bonded with a 250°F cure elastomer modified epoxy adhesive. One set of coupons was primed with BR 123 primer (a non-corrosion inhibiting primer) while the other set was primed with... 

The largest application for hot-roll-bonded materials—alclad aluminum—also falls into this category. In this case, a more active aluminum alloy is bonded to a more noble aluminum alloy. In service, the outer clad layer of aluminum corrodes sacrificially and protects the more noble aluminum substrate. 

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. 

It should be noted that a number of aluminum alloys are available (see Table 28-16). Many have improved mechanical properties over pure aluminum. The wrought heat-treatable aluminum alloys have tensile strengths of 90 to 228 MPa (13,000 to 33,000 Ibf/in ) as annealed when they are fuUy hardened, strengths can go as high as 572 MPa (83,000 Ibf/in"). However, aluminum alloys usually have lower corrosion resistance than the pure metal. The alclad alloys have been developed to overcome this snortcoming. Alclad consists of an aluminum layer metaUurgicaUy bonded to a core alloy. 

The Alclad alloys have been developed to overcome this shortcoming. Alclad consists of a pure aluminum layer metallurgically bonded to a core alloy. The corrosion resistance of aluminum and its alloys tends to be very sensitive to trace contamination. Very small amounts of metallic mercury, heavy-metal ions, or chloride ions can frequently cause rapid failure under conditions which otherwise would be fully acceptable. When alloy steels do not give adequate corrosion protection—particularly from sulfidic attack—steel with an aluminized surface coating can be used. 

Fresh water. Aluminum and its alloys are not prone to corrosion on exposure to distilled water up to 180°C. Thus storage tanks, piping and fittings of the alloy can be used for handling distilled water. The composition of natural fresh water is variable. In spite of this restriction, the alloys are not attacked, even at 180°C in natural waters. It should be noted that pitting may occur when a small thickness of the sample is exposed. In this case Alclad 3003 is recommended for use to avoid failure due to pitting. 

Atmospheric Corrosion. The aluminum-based alloys in general are corrosion resistant to outdoor exposure with the exception of copper-bearing alloys. The Alclad alloys gave the best performance. The loss in tensile strength has been used as a measure of corrosivity and the loss of 1-2% of tensile strength over a period of 1 yr and in particular a loss of 17% was observed with 2017T alloy in 1 yr of outdoor exposure. 

The aluminum-based alloys such as 1100, 3300, 5052, 6053, Alclad 3300, Alclad 1017-T and Alclad 20-24-T are highly resistant to most natural environments alloys of thickness <0.076 mm should not be used. Lead and bismuth added to alloys 2021 and 6262 improve chip breakage and other machining characteristics. 

Some measures involving cathodic protection of aluminum using zinc as the sacrificial anode,47 and protection of aluminum ship hulls are found in the literature.37 Overprotection may lead to alkali (cathodic corrosion) attack. Alclad alloy systems are also some form of self-contained cathodic protection systems. 

Figure 28.2 shows the typical images of three Alclad panels (an aluminum alloy clad with nearly pure aluminum) tested with SO2 salt spray. The panels are (1) chromate conversion coated followed by priming with E-coat (2) chromate conversion coated followed by priming with Deft (chromated spray paint) and (3) plasma coated followed by priming with E-coat. The corroded area and corrosion width are also given in the figure. 

Figure 28.20 Changes of Bode plots as a function of immersion time for freestanding Parylene C film and Parylene C coated Alclad 7075-T6 aluminum sheets in 0.9% NaCl solution 0.1 day indicates the initial run after 2h immersion of the samples.

Alclad is an aluminum alloy clad with a nearly pure aluminum. The base alloy is AA 2024-T3, and the cladding has a specified composition of, in wt%, Cu 0.1, Si + Fe 0.7, Mg 0.05, Mn 0.05, Zn 0.1, Ti 0.03, others 0.3, and A1 the balance [9]. This Alclad is designated as 2A in this chapter, i.e., 2 representing 2024 T3 alloy and A representing Alclad. The pure aluminum has an excellent corrosion resistance. The clad is used to protect the base aluminum alloy from corrosion. 

Some of the alloys of aluminum are very useful. Duralumin or dural is an alloy (containing 95.5 /, aluminum, 3% copper, 1% manganese, and 0.5% magnesium) which is stronger and tougher than pure aluminum. It is less resistant to corrosion, however, and often is protected by a coating of pure aluminum. Plate made by rolling a billet of dural sandwiched between and welded to two pieces of pure aluminum is called Alclad plate (Fig. 9.5). 

Aluminum alloys Aluminum Alclad Cadmium Mild steel Cast iron Ni-Resist... 

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