Hard anodizing

Hard anodic films, 50-100/rm thick, for resistance to abrasion and wear under conditions of slow-speed sliding, can be produced in sulphuric acid electrolytes at high current density and low temperature. Current densities range from 250 to 1 000 Am , with or without superposed alternating current in 20-100g/1 sulphuric acid at —4—I- 10°C. Under these conditions, special attention must be paid to the contact points to the article under treatment, in order to avoid local overheating. 

Hard Anodic Oxide Coatings on Aluminium for Engineering Purposes, British Standard 5599 1978... 

CAS 89-08-7 EINECS/ELINCS 201-881-6 Uses Electrolytic bath additive for production of hard anodic oxide coatings on aluminum and aluminum-based alloys colored coalings are abrasion resist, and attractive for architectural and other uses Features Colors depend on base metal composition, current dens., voltage, film thickness and electrolyte composition, particularly sulfate and aluminum contents Properties 49-51% act. 

Lee, W., Ji, R., Gosele, U., Nielsch, K. Fast fabrication of long-range ordered porous alumina membranes by hard anodization. Nat. Mater. 5, 741-747 (2006)... 

Increase surface hardness and wear resistance Hard anodizing... 

Anodizing at very low temperature, almost 0°C, may give layer thicknesses up to 100 pm with low porosity. The method is called hard anodizing. The surfaces obtained are in fact not harder than ordinary anodized films, but due to the great layer thickness they are characterized by good wear and corrosion resistance. 

Fig. 23. TEM pictures of a standard type lit hard anodization (left) and a mixed acid anodization (right) [80]...

H. Shih, D. Outka, and J. Daugherty, "Specification for Hard Anodized Aluminum... 

Hard anodizing for engineering applications, c.g. cylinder linings boat winches... 

Bearing Plate 6061-T6 Aluminium Alloy-Hard Anodized,... 

A1 or Pb 40-60 Transparent and near-colourless Hard anodizing (as above)... 

The relatively low abrasion and wear resistance of aluminum can be compensated by an appropriate surface treatment so that sufficient life times can be achieved. Hard anodizing, chemical nickel plating, chrome plating, and special chemical coatings, which facilitate demolding, have proven their worth. 

They have good corrosion resistance. Therefore, one can do without expensive surface treatments. However, it is possihie to chrome plate, nickel plate, or hard anodize aluminum plates after machining (electrical discharge machining [EDM]). 

Hard anodized layers are partially applied or on all sides to serve both the corrosion and the wear protection. 

Hard anodizing is suitable for aluminum alloys. It enables the production of extremely hard surfaces (about 350 HV). In contrast to the coatings, the anodic oxide layer is formed from the metal itself (which is why there are no adhesion problems). 

The corresponding values for ALUMOLD are about the same, especially after hard-anodizing, which is performed on the finished mold. It must be considered that the hard anodized layer grows to about 50% of its thickness beyond the initial surface and about 50% into the metal. In the development of such molds, specialists for hard anodizing should be consulted. 

Bartak, D E, Lemieux, B E Woolsey, E R (1995), Hard anodic coating for magnesium alloys. US Patent 5470664. 

COMA (2001), A hard anodic coating for magnesium [Online]. Luke Engineering MFG Co. Available http //www.lukeng.com/magoxid.htm [Accessed April 19 2(X)1]. 

British Standards Institute, BS 5599 (1993). Specification for Hard Anodic Oxidation Coatings on Aluminium and Its Alloys for Engineering Purposes. 

Arrowsmith, D. J., CUlford, A. W., Davies, R. J., Moth, D. A. (1984). Durability of adhesively bonded aluminium pretreated by hard anodizing followed by a phosphoric acid dip. Extended abstracts for the international adhesive conference. PRI, London. 

Nonreactive materials include glass, stainless steel, ceramic, enamel, and hard anodized aluminum. Reactive materials include (non-stainless) steel, cast-iron, copper, and aluminum. These materials conduct heat evenly and are excellent for boiling water, frying burgers, or making stock. But if you re working with acidic or alkaline ingredients, stick to nonreactive cookware. 

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