Resistance magnesium alloys

Manganese(II) chloride is utilized in the manufacture of corrosion resistant magnesium alloys, for the coloring of bricks and in dry batteries. 

Sivaraj D, McCune R, Mallick P K and Mohanty (2006), Aqueous corrosion of experimental creep-resistant magnesium alloys , 2006 SAE World Congress, SAE Paper No. 2006-01-0257. 

Some tests indicate that magnesium alloys are resistant to loam sod. However, in the presence of chlorides, corrosive attack may be serious particularly if galvanic couples are present as a result of coupling to iron stmctures. 

Contact of brass, bronze, copper or the more resistant stainless steels with the 13% Cr steels in sea-water can lead to accelerated corrosion of the latter. Galvanic contact effects on metals coupled to the austenitic types are only slight with brass, bronze and copper, but with cadmium, zinc, aluminium and magnesium alloys, insulation or protective measures are necessary to avoid serious attack on the non-ferrous material. Mild steel and the 13% chromium types are also liable to accelerated attack from contact with the chromium-nickel grades. The austenitic materials do not themselves suffer anodic attack in sea-water from contact with any of the usual materials of construction. 

In considering the corrosion of magnesium and its alloys it is important to examine the methods available for assessing corrosion tendencies and particularly those known as accelerated tests. Tests carried out by immersion in salt water or by spraying specimens regularly with sea-water are worthless as a means of determining the resistance of magnesium alloys under any other than the particular test conditions. Extrapolation to less corrosive conditions is not valid and even the assessment of the value of protective measures by such means is hardly possible. The reason is to be found in the fact that corrosion behaviour is directly related to the formation of insoluble... 

By the use of many commercial abrasive processes, the corrosion resistance of magnesium alloys can be reduced to such an extent that samples of metal that may lie quiescent in salt water for many hours will, after shot blasting, evolve hydrogen vigorously, and the corrosion rate, as measured by loss of weight, will be found to have increased many hundred-fold. The effect in normal atmospheres is naturally much less, yet the activation of the surface is an added hazard and is the opposite of passivation which is essential if later-applied paint finishes are to have proper durability. 

Rapid solidification technology has been applied to several magnesium alloy systems and extruded material of some of these systems have exhibited excellent corrosion resistance. 

King, J. F., Adamson, K. G. and Unsworth, W., Impregnation of Anodic Films for the Protection of Magnesium Alloys, Ministry of Defence D.Mat. Report No. 193, February (1973) Adamson, K. G., King, J. F. and Unsworth, W., Evaluation of High Temperature Resistant Coatings for the Protection of Magnesium Alloys, Ministry of Detence D.Mat. Report No. 196, July (1973)... 

Aluminum-magnesium alloys, 2 311 chemical industry applications, 2 341 corrosion resistance, 2 336 finishes, 2 338... 

Swedish chemist Jons Jakob Berzelius Radioactive metal named for Thor, the ancient Scandinavian god of war promising as a future source of nuclear energy makes magnesium alloys heat resistant. 

Tellurium has been recommended as an additive to magnesium to increase corrosion resistance (see Corrosion and corrosion CONTROL). The addition is highly exothermic but can be controlled by adding one tellurium tablet at a time to a sufficiently large bath of liquid magnesium. The addition to tellurium and chromium improves the stress-corrosion resistance of aluminum—magnesium alloys. 

Post-Treatments. Although many post-treatments have been used over plated metals, chromate conversion coatings remain as the most popular. Chromates are used to improve corrosion resistance, provide good paint and adhesive base properties, or to produce brighter or colored finishes. Formulations are usually proprietary, and variations are marketed for use on zinc, zinc alloys, cadmium, copper and copper alloys, and silver (157). Chromates are also used on aluminum and magnesium alloys (158,159). More recently, chromate passivation has been used to extend salt spray resistance of autocatalytic nickel plated parts. 

Cast magnesium alloys used for structural applications comprise a highly heterogeneous ductile matrix with several dominant types of inclusions that dictate fatigue resistance. We use the term inclusion as distinctly different from a crack, as the former occurs naturally as products of the casting process, while the latter is... 

Various concentrations and purities of aqueous ammonia are on the market. The typical concentration is 25% to 30% ammonia and the iron content is less than 10 ppm. If the ammonia content is above 25%, it must be shipped in pressure vessels because of its elevated vapor pressure. For more stringent purity requirements for aqueous ammonia, the containers should be made of seawater-resistant aluminum (magnesium alloyed) or austenitic steels74. 

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