Anodes, aluminum magnesium

On the anodic side chlorine is formed, which reacts with all anode materials known so far. At first we used mercury later on several research teams used aluminum, magnesium, copper, etc., [20]. All these are sacrificial anodes and the corresponding chlorides were formed. Graphite shows rapid passivation. Silicon with a small copper content for better conductivity reacts with the removal of the copper, and the conductivity decreases. 

This method uses a more active metal than that in the structure to be protected, to supply the current needed to stop corrosion. Metals commonly used to protect iron as sacrificial anodes are magnesium, zinc, aluminum, and their alloys. No current has to be impressed to the system, since this acts as a galvanic pair that generates a current. The protected metal becomes the cathode, and hence it is free of corrosion. Two dissimilar metals in the same environment can lead to accelerated corrosion of the more active metal and protection of the less active one. Galvanic protection is often used in preference to impressed-current technique when the current requirements are low and the electrolyte has relatively low resistivity. It offers an advantage when there is no source of electrical power and when a completely underground system is desired. Probably, it is the most economical method for short life protection. 

C. Chemical modification of the glued surfaces by the formation of passivating layers. The modification technique depends on the nature of the metal. The parts are most often subjected to acid pickling, e.g. aluminum alloys are anodized in sulfuric and chromic acids. It is preferable to anodize aluminum parts in sulfuric acid followed by treatment of the anodic film in a bichromate. There are several methods of pickling carbon and stainless steels, chemical oxidation of magnesium alloys as well as copper and titanium alloys before gluing [4]. 

Fig. 7 X-ray photoelectron spectrometer. Left schematic view of a SSX 100/206 (Surface Science Instruments). Right, photographs of a Kratos Axis Ultra (Kratos Analytical) with the introduction and intermediate chambers (top) and analysis chamber (bottom), a, Turbomolecular pump b, cryogenic pump c, introduction chamber d, sample analysis chamber (SAC) e, transfer probe f, automatized X, Y, Z manipulator g, X-ray monochromator h, electrostatic lens i, hemispherical analyzer (HSA) j, ion gun k, aluminum anode (with monochromator) 1, aluminum-magnesium twin anode m, detector. Left channel plate. Right 8 channeltrons (Spectroscopy mode), phosphor screen behind a channel plate with a video camera (Imaging mode) n, spherical mirror analyzer (SMA) o, parking facility in the sample transfer chamber p, sample cooling device for the introduction chamber q, sample transfer chamber r, monitor interconnected with the video camera viewing samples in the SAC s, video camera in the SAC t, high temperature gas ceU (catalyst pretreatment)...

As explained in Chap. 14, anodizing is a widely use technique to produce a protective inorganic coating of some engineering materials such as aluminum, magnesium, titanium and a few other metals and alloys by the application of an anodic potential that would be normally quite corrosive if it was not for the barrier created by the process itself. Of all metals that are routinely anodized, aluminum alloys are... 

Takaya, M (1987), Anodizing of magnesium alloy in potassium hydroxide-aluminum hydroxide solutions . Keikinzoku, 37, 581-586. 

Pieces of metal which, being anodic to the equipment into which they are introduced, will galvanically corrode and so protect the equipment. Cathodic protection, based on wasting of anodic metal to prevent corrosion of cathodic metal - zinc, aluminum, magnesium, carbon steel, etc. - so protecting steel and other more noble metals. 

Corrosion activity may develop because of some heterogeneity in the grain boundary structure. In aluminum-copper alloys, precipitation of AI2CU particles at the grain boundaries leaves the adjacent solid solution anodic and more prone to corrosion. With aluminum-magnesium alloys, the opposite situation occurs, since the precipitated phase Mg Als is less noble than the solid solution. Serious intergranular attack in these two alloys may however be avoided, provided that correct manufacturing and heat treatment conditions are observed. 

In natural environments, including saline conditions, zinc is anodic to aluminum and corrodes preferentially, giving protection to aluminum. Magnesium is similarly protective, although in severe marine environments it causes cathodic corrosion of aluminum because of an alkaline condition produced on the aluminum surface. Cadmium is neutral to aluminum and can safely be used in contact with it. The other stmc-... 

F.F. Booth and H.P. Godard, An Anodic Stress-Corrosion Test for Aluminum-Magnesium Albys, First International Congress on Metallic Corrosion, Butterworths, 1962, p 703-712... 

Electroreductive coupling of ben2otrifluorides with sacrificial aluminum or magnesium anodes in the presence of acetone, carbon dioxide, or /V, /V-dimethylformamide provides a novel route to ArCF2-derivatives (310). 

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