Secondary magnesium alloys

Blawert C, Morales GED, Dietzel W, Kainer KU, Scharf C, Ditze A, (2006), Influence of the copper content on microstructure and corrosion resistance of AZ91 based secondary magnesium alloys , SAE paper 2006-01-0254. 

Scharf C, Ditze A, Shkurankov A, Morales GED, Blawert C, Dietzel W, Kainer KU, (2005), Corrosion of AZ 91 secondary magnesium alloy . Advanced Engineering Materials, 1, 1134-1142. 

Uses Alone as incendiary agent or as primary igniting incendiary for secondary incendiary material such as heavy hydrocarbons, or for igniting the casing of incendiary bombs made of a magnesium alloy. 

Aluminum Powder Flaked, Grained and Atomized" (for use in ammunition) 2)US Spec JAN-A-512, "Aluminum Powdered" (Grained or Atomized)(from secondary metal) (for use in pyrotechnics or in incendiary "thermite") 3)US Spec JAN-A-667, "Aluminum Powder, Superfine" 4)US Spec JAN-M-454, "Magnesium-Aluminum Alloy, Powdered" 5)W.W.Scott N.H.Furman, "Standard Methods of Chemical Analysis, "Van No strand, NY(1939) 6)H.V. Churchill... 

This chapter presents electrochemical reactions and corrosion processes of Mg and its alloys. First, an analysis of the thermodynamics of magnesium and possible electrochemical reactions associated with Mg are presented. After that an illustration of the nature of surface films formed on Mg and its alloys follows. To comprehensively understand the corrosion of Mg and its alloys, the anodic and cathodic processes are analyzed separately. Having understood the electrochemistry of Mg and its alloys, the corrosion characteristics and behavior of Mg and its alloys are discussed, including self-corrosion reaction, hydrogen evolution, the alkalization effect, corrosion potential, macro-galvanic corrosion, the micro-galvanic effect, impurity tolerance, influence of the chemical composition of the matrix phase, role of the secondary and other phases, localized corrosion and overall corrosivity of alloys. 

Galvanic corrosion or bimetallic corrosion is important to consider since most of the structural industrial metals and even the metallic phases in the microstructure alloys create galvanic cells between them and/or the a Mg anodic phase. However, these secondary particles which are noble to the Mg matrix, can in certain circumstances enrich the corrosion product or the passive layer, leading to a decrease or a control of the corrosion rate. Severe corrosion may occur in neutral solutions of salts of heavy metals, such as copper, iron and nickel. The heavy metal, the heavy metal basic salts or both plate out to form active cathodes on the anodic magnesium surface. Small amounts of dissolved salts of alkali or alkaline-earth metal (chlorides, bromides, iodides and sulfates) in water will break the protective film locally and usually lead to pitting (Froats et al., 1987 Shaw and Wolfe, 2005). 

---