Anodic oxidation of valve metals, particularly, aluminum, has attracted considerable attention because of its wide application in various fields of technology. Traditionally, aluminum is “anodized” in order to protect the metal against corrosion, to improve its abrasion and adsorption properties, etc.1 The more recent and rapidly growing applications of anodic aluminas in electronics are due to their excellent dielectric properties, perfect planarity, and good reproducibility in production. Finally, ways have recently been found to use the energy potential of aluminum oxidation for chemical power sources of the metal-air type2,3 and other electrochemical applications.

Electrochemistry of Aluminum in Aqueous Solutions and Physics of Its Anodic Oxide

Surface conduction mechanisms and the electrical properties of Al2O3 humidity sensor

Post-oxidising treatments can be performed to improve the corrosion resistance of nitrided steel components. The glow-discharge process appears particularly attractive, since it allows to carry out both nitriding and post-oxidising treatments in a single technological operation, simply varying the treatment atmosphere and the working conditions. In the present paper the effects of using air as the treatment atmosphere of glow-discharge post-oxidising treatment have been evaluated. Nitriding treatments were performed at 773 K for 5 h, and post-oxidising treatments were carried out at 623 and 773 K for 1 h. The nitriding and nitriding+post-oxidising treatments produce modified surface layers consisting of an outer compound layer and an inner diffusion layer. When the post-oxidising treatments are performed, the compound layer consists of an oxide layer on the top of the nitride layer. With a 623 K post-oxidising treatment the oxide layer consists mainly of magnetite, Fe 3 O 4 , while when post-oxidising is carried out at 773 K it consists essentially of hematite, Fe 2 O 3 . In the inner nitride layer iron (γ′-Fe 4 N, e-Fe 2–3 N) and chromium (CrN) nitrides are present. In all the treated samples high hardness values are obtained in the modified layers. The hardness profiles of the post-oxidised samples are only slightly affected by the 773 K post-oxidising treatment. The corrosion resistance of the treated samples was tested and the results show that the nitriding+623 K post-oxidising treatment is able to significantly improve the corrosion resistance of the untreated and treated AISI H11 samples.

Glow-discharge nitriding and post-oxidising treatments of AISI H11 steel

Duplex treatment of plasma nitriding and plasma oxidation of plain carbon steel

Surface preparation techniques of aluminium for adhesive joining in aerospace applications and their influence on bond formation have been reviewed. The mechanisms of the different pretreatments have been discussed with attention to the effect of alloying elements and conditions of the technique. On the basis of the morphology and physical and chemical state of the metal surface it has been attempted to characterize the adhesive-metal bond, its strength, and stability under adverse conditions.MST/546

I.E. Klein

Papers

Structure and corrosion resistance of oxides grown on maraging steel in steam at elevated temperatures

Oxide treatments of Al 1100 for adhesive bonding. Surface characterization

Chemical interaction in the system aluminum oxide-primer-adhesive

Chemical interactions in the system anodized aluminum—primer—adhesive