Intergranular corrosion, while walking between the microcrystals of metal, the metal eventually disintegrate. It is related to chromium carbide precipitation along the joints. For it to occur, three conditions must be met: at least 0.035% carbon, sensitization by holding at a temperature of 400 to 800 degrees C, an acidic external environment with an oxidizing power between two defined limits. Pitting corrosion is usually not due to heterogeneity of material but the unintended presence of metallic dust, wet, form a battery (stainless steel fabricator). The steels surface then constitutes the anode and corrodes. There can be 2 mm thick pieces within hours. An environment that is both highly acidic and very oxidizing can produce similar effects.
Other elements may be added, in particular nickel, which improves the mechanical properties in general and particularly ductility, and other elements such as molybdenum or titanium, which enhance the stability of alloy at temperatures other than room as well as elements with high melting points such as vanadium and tungsten in general accompanied by an increase in chromium content, for resistance to high temperatures ignited (refractory steels).
The corrosion of metals are electrochemical in nature: the metal returns to its thermodynamically stable state, the oxidized state. In presence of an oxidizing environment (water, air), the metal reacts with the environment, this reaction taking place with exchange of electrons. Iron, major constituent of steels, is easily oxidized; the corrosion product, rust, crumbles or dissolved in water, creating a deterioration of part. When hot, the diffusion of oxidants atoms in metal thickness can further complicate the problem.
In 1890s, the German Hans Goldschmidt developed and patented a process called thermite which allowed to obtain carbon-free iron. Between 1904 and 1911, various researchers, including the French Leon Guillet, devised various alloys that could today be considered stainles. In 1911, German Philip Monnartz highlighted the influence of chromium alloys rate and resistance to corrosion.
Manganese is a nickel substitute. Some series of austenitic alloys have been developed to deal with supply of nickel6 uncertainties. Molybdenum and copper improve the resistance in most corrosive environments, particularly those that are acidic, but also in phosphate solutions, sulfur, etc. Molybdenum increases the stability of passivation films.
There are actually numerous grades of stainles-steels and the choice is difficult because they do not all have the same behavior in a given environment. Are often referred to by the weight percentages of nickel and chromium. Thus, a 18/10 stainles-steel, such as those used in cutlery for cutlery and for cooking in general, contains 18% by weight of chromium and 10% by weight of nickel.
Niobium has a melting point much higher than titanium and has similar properties. It is used in filler metals for welding arc instead of titanium which is volatilized during transfer in arc. Silicon also plays a role in oxidation resistance, especially vis-a-vis the strong oxidizing acid (concentrated nitric acid or concentrated sulfuric acid chaud.
The metal is exposed (grinding, machining, deformation of workpiece cracking the passive layer, friction, erosion, cavitation), but the oil or grease prevents air arriving to oxidize; then the surface is "active". Non-stainles-steel particles pollute the surface (pollution iron): these particles rust, forming halos, but can also initiate corrosion of stainless-steel in some cases.
Other elements may be added, in particular nickel, which improves the mechanical properties in general and particularly ductility, and other elements such as molybdenum or titanium, which enhance the stability of alloy at temperatures other than room as well as elements with high melting points such as vanadium and tungsten in general accompanied by an increase in chromium content, for resistance to high temperatures ignited (refractory steels).
The corrosion of metals are electrochemical in nature: the metal returns to its thermodynamically stable state, the oxidized state. In presence of an oxidizing environment (water, air), the metal reacts with the environment, this reaction taking place with exchange of electrons. Iron, major constituent of steels, is easily oxidized; the corrosion product, rust, crumbles or dissolved in water, creating a deterioration of part. When hot, the diffusion of oxidants atoms in metal thickness can further complicate the problem.
In 1890s, the German Hans Goldschmidt developed and patented a process called thermite which allowed to obtain carbon-free iron. Between 1904 and 1911, various researchers, including the French Leon Guillet, devised various alloys that could today be considered stainles. In 1911, German Philip Monnartz highlighted the influence of chromium alloys rate and resistance to corrosion.
Manganese is a nickel substitute. Some series of austenitic alloys have been developed to deal with supply of nickel6 uncertainties. Molybdenum and copper improve the resistance in most corrosive environments, particularly those that are acidic, but also in phosphate solutions, sulfur, etc. Molybdenum increases the stability of passivation films.
There are actually numerous grades of stainles-steels and the choice is difficult because they do not all have the same behavior in a given environment. Are often referred to by the weight percentages of nickel and chromium. Thus, a 18/10 stainles-steel, such as those used in cutlery for cutlery and for cooking in general, contains 18% by weight of chromium and 10% by weight of nickel.
Niobium has a melting point much higher than titanium and has similar properties. It is used in filler metals for welding arc instead of titanium which is volatilized during transfer in arc. Silicon also plays a role in oxidation resistance, especially vis-a-vis the strong oxidizing acid (concentrated nitric acid or concentrated sulfuric acid chaud.
The metal is exposed (grinding, machining, deformation of workpiece cracking the passive layer, friction, erosion, cavitation), but the oil or grease prevents air arriving to oxidize; then the surface is "active". Non-stainles-steel particles pollute the surface (pollution iron): these particles rust, forming halos, but can also initiate corrosion of stainless-steel in some cases.
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