Corrosion resistance treatment

Voevodin, NN, Grebasch, NT, Soto, WS, Kasten, LS, Grant, JT, Arnold, FE, Donley, MS. 2001. An Organically Modified Zirconate Film as a Corrosion Resistant Treatment for Aluminum 2024-T3. Prog. Org. Coat., 41, 287. 

Either process lends itself to the use of a significant variety of aluminium foils. For example, the HexWeb (originally Aeroweb) range of honeycombs uses 3003, 5052 and 5056 alloys - the aerospace grades having a corrosion-resistant treatment (for example, HexWeb CR-PAA/CRIII 5052). The expanded process is also particularly suited to a variety of non-metallic foil materials. 

Parkhill R. L., Knobbe E. T. and Donley M. S. (2001), Application and evaluation of environmentally comphant spray-coated ormosU films as corrosion resistant treatments for aluminum 2024-T3 , Prog. Org. Coat, 41,261-5. 

Voevodin N. N., Grebasch N. T., Soto W. S., Kasten L. S., Grant J. T. et al. (2001b), An organically modified zirconate film as a corrosion-resistant treatment for aluminum... 

Optimum surface roughness usually is 0.05—0.5 pm a very smooth surface contains very Htde lubricant within its depressions, whereas rough peaks penetrate the lubricant to promote wear. Improved corrosion resistance may be obtained with a suitable subcoating surface conversion treatment or by inclusion of inhibitors in the coating. 

Cladding and backing metals are purchased in the appropriately heat-treated condition because corrosion resistance is retained through bonding. It is customary to supply the composites in the as-bonded condition because hardening usually does not affect the engineering properties. Occasionally, a post-bonding heat treatment is used to achieve properties required for specific combinations. 

Steam treatment imparts increased corrosion resistance for ferrous P/M parts. The parts are heated to 400—600°C and then exposed to superheated steam. After cooling, the parts are usually oil dipped to further increase corrosion and wear resistance, and to enhance appearance (see Corrosion and CORROSION control). Heat treated parts are seldom steam treated because annealing reduces hardness and tensile strength. 

Chemical treatments commonly appHed to cormgated paperboard packaging materials include additives that impart various degrees of water resistance, humidity resistance, oil and grease resistance, product abrasion resistance, product corrosion resistance, adhesion release properties, flame-retardant properties, nonskid properties, and static electricity control properties to the finished package (1,2). 

Most wrought alloys are provided in conditions that have been strengthened by various amounts of cold work or heat treatment. Cold worked tempers are the result of cold rolling or drawing by prescribed amounts of plastic deformation from the annealed condition. Alloys that respond to strengthening by heat treatment are referred to as precipitation or age hardenable. Cold worked conditions can also be thermally treated at relatively low temperatures to affect a slight decrease in strength (stress rehef annealed) to benefit other properties, such as corrosion resistance and formabiUty. 

Corrosive chemicals and external exposure can cause tank failure. Materials of construction should be chosen so that they are compatible with the chemicals and exposure involved. Welding reduces the corrosion resistance of many alloys, leading to localized attack at the heat-affected zones. This may be prevented by the use of the proper alloys and weld materials, in some cases combined with annealing heat treatment. 

Ferritic stainless contains 15 to 30 percent Cr, with low carbon content (0.1 percent). The higher chromium content improves its corrosive resistance. Type 430 is a typical example. The strength of ferritic stainless can be increased by cold working but not by heat treatment. Fairly ductile ferritic grades can be fabricated by all standard methods. They are fairly easy to machine. Welding is not a problem, although it requires skilled operators. 

Austenitic stainless steels are the most corrosion-resistant of the three groups. These steels contain 16 to 26 percent chromium and 6 to 22 percent nickel. Carbon is kept low (0.08 percent maximum) to minimize carbide precipitation. These alloys can be work-hardened, but heat treatment will not cause hardening. Tensile strength in the annealed condition is about 585 MPa (85,000 Ibf/in"), but workhardening can increase this to 2,000 MPa (300,000 Ibf/in"). Austenitic stainless steels are tough and ducdile. 

This is the final neutralizing rinse after the pre-treatment to obtain a better corrosion resistance. The phosphated surfaces are treated with chromic acid-based or acidified sodium dichromate solutions which are not affected by moisture and thus protect the phosphate coating. 

Corrosion resistance Design of treatment/disposal plant... 

CAA. Chromic acid anodization [74-76]. was developed initially as a treatment to improve the corrosion resistance of aluminum surfaces, but it is also used as a surface treatment for adhesive bonding especially in Europe where it is used extensively in aerospace applieations [29,77],... 

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