Aluminum chemical surface treatments

Calorising Also spelled Calorizing. A proprietary process for protecting the surface of iron or steel by applying a layer of aluminum. Several methods of application may be used dipping, spraying, or chemical reaction with aluminum chloride. See also metal surface treatment. 

One very beneficial chemical pretreatment treatment for aluminum substrates is phosphoric acid anodization (PAA), which provides an oxide coating that is inherently hydration-resistant. Its stability is due to a layer of phosphate incorporated into the outer A1203 surface during anodization. 

The results of our extensive research on the hydrolysis of AIN powder improved our understanding of the reactions and mechanisms as well as giving us the possibility to control the hydrolysis reactions by chemical means. Using phosphoric acid, we made it possible to control the start and the speed of the reaction for use in the HAS forming process, which exploits hydrolysis for the solidification of aqueous slurries. On the other hand, with proper surface treatment using aluminum dihydrogen phosphate, water-resistant AlN powder can be prepared, that is hydrophilic, which... 

S. Wemick, R. Pinner, P. G. Sheasby, Chemical conversion coatings. The Surface Treatment and Finishing of Aluminum and its Alloys, 5th ed., ASM International, Metals Park, Ohio, 1987, pp. 220-284, Vol. 1. 

The most common surface treatments are grit blasting or other mechanical abrasion processes that clean the surface and provide a more chemically reactive oxide. Although the result is not as good as that of the common aluminum and titanium treatments. 

Before the anode potential measurements, the anodes were initially conditioned by electrolysis (chemical conversion treatment) applying a 160 g/1 H2SO4 electrolyte at 40 C and a current density of 50 mA/cm for 24 h in order to prepare a Pb02 oxide layer at the anode surface. The distance between the anode and cathode in the chemical conversion treatment was 3 cm. After the chemical conversion treatment, the anode potential was measured in a 160 g/1 H2SO4 and 60 g/1 Zn electrolyte at a current density of 50 mA/cm for 1,0 h. The experiment temperature was 40° C and the anode-cathode distance was 3 cm. Another experiment with the same characteristics as above mentioned, but without Zn in the electrolyte and with no preliminary electrolysis, was performed for 20 days electrolysis time, the electrolyte being replaced every two days. The aluminum cathode used in the experiments had a surface area of... 

From Tables 9.8 and 9.9, it can be forecast that epoxy adhesives will wet dean aluminum or copper surfaces. However, epoxy resin will not wet a substrate having a critical surface tension significantly less than 47 dyn/cm. Epoxies will not, for example, wet either a metal surface contaminated with silicone oil or a clean polyethylene substrate. For wetting to occur, the substrate surface has to be chemically or physically altered by some mechanism to raise its surface energy. This is why there are so many prebond surface treatments for plastic substrates. 

Aluminum trihydrate is available in a variety of grades that differ in particle size, color, and surface treatment. ATH finds use in such resins as polyesters, epoxies, and polyvinyl chloride (PVC). Commercial manufacturers of ATH include Akochan Corp. Alcoa Industrial Chemicals Pluess-Staufer International Inc. and Whittaker, Clark Daniels. 

In the chloride process, dried ore reacts with chlorine gas to produce titanium tetrachloride. The titanium tetrachloride is purified chemically and by distillation and then reacted with oxygen to form titanium dioxide and chlorine. The chlorine is recycled. Prior to the oxidation, a minor amount of aluminum chloride is added to promote rutile formation [22]. The rutile is preferred because it is more durable and has a higher refractive index. Untreated titanium dioxide is used, but more commonly a surface treatment is done to improve specific end-use property requirements such as ability to disperse or weather resistance. 

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. 

Non-ferrous metals may form a protective oxide layer, providing a barrier against further deterioration. The coating of aluminum, magnesium, copper, chromium, cadmimn and tin may be required, nevertheless, to protect the surface from deterioration other than oxidation, or a clear coat may be used to preserve the appearance of the virgin metal from oxidation. Zinc surfaces may require a chemical pre-treatment prior to the application of the primer and top coat, depending on the condition of the surface and type of primer used. Lead and lead alloy surfaces are easily coated with a linseed oil based primer and a compatible top coat. 

Abstract Proper treatment of an adherend surface is one of the most important factors in assuring high initial strength and extended durability of high-performance adhesive joints. There are several requirements for a good surface preparation (1) The surface must be cleaned of any contamination or loosely bound material that would interfere with the adhesive bond. (2) The adhesive or primer must wet the adherend surface. (3) The surface preparation must enable and promote the formation of chemical and/or physical bonds across the adherend/ primer-adhesive interface. (4) The interface/interphase must be stable under the service conditions for the lifetime of the bonded structure. (5) The surface formed by the treatment must be reproducible. In this chapter, high-performance surface treatments for several metals and other materials are discussed. Surface treatments of aluminum and other metals are used to illustrate how proper surface preparations meet these requirements. 

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