On a copper cathode recovered protons H + : The following electrochemical reaction occurs : Sulfuric acid is completely dissociated in water (since it is a strong acid) by the formation of H ions +, which define the acidity of the medium. Liquid, thus, provides an ionic electrical connection (Figure 9).įigure 9 - Principle of a galvanic cell įigure 1 shows cell, wherein the electrolyte is a sulfuric acid solution. Inside the fluid transfer occurs by electric current the ions move. These two electrodes connected to an electrical circuit outside, electrons which circulates. Electrolyte - is usually a dilute acid solution, for example, sulfuric acid, or saline, for example, copper sulfate. These two electrodes are immersed in the conductive liquid, which is called an electrolyte. Galvanic corrosion works like a battery, which consists of two electrodes: Corrosive to aluminum has a uniform character, it develops in the depths of craters, which have a more or less rounded shape [3 [.Īll aluminum alloys are subject to identical galvanic corrosion. Galvanic corrosion is localized in dense aluminum contact area with another metal. This corrosion is not to scatter all over the surface of the product, as is the case with the point - pitting - corrosion. The appearance of galvanic corrosion is very characteristic. Galvanic corrosion may occur with any metal, as soon as the two different metals are in contact in an electrically conductive liquid. This type of corrosion is different from the types of corrosion, that might arise, if both of these metals were placed separately into the same liquid. Other metal will not corrode, conversely, it will be protected from this type of corrosion. When two different metals come in direct contact with the electroconductive liquid, experience shows, that one of them can corrode, ie corrode. Under these conditions, the potential difference between dissimilar metals produces electric current, passing through the electrolyte, which (current) leads to corrosion primarily of the anode or less noble metal from this pair. Galvanic or electrochemical corrosion occurs, when two dissimilar metals form an electrical circuit, closes the liquid electrolyte or a film or a corrosive environment. The most frequent errors aluminum structural design associated with galvanic corrosion. Moreover, improper use of aluminum parts and products can exacerbate corrosion processes. ![]() With another, more “honorable” metal, such as copper įigure 7 – Pitting (pitting) corrosion of aluminumįigure 8 – Intergranular corrosion and subsurface corrosion ĭepending on the environmental conditions, loading and functionality details of any of the types of corrosion can cause premature failure. ![]() It occurs under conditions of wet or wet contact Solutions of strong alkalis and some acids įigure 3 – Crevice corrosion of aluminum įigure 4 – Fretting corrosion of aluminum: mutual friction of two aluminum componentsįigure 5 – Corrosion of aluminum alloys under stress: under certain conditionsįigure 6 – Galvanic corrosion of aluminum alloy The main source of protection against corrosion is strong, self-healing oxide film, which is always present on aluminum in an ambient air atmosphere (Figure 1).įigure 1 – Natural aluminum corrosion protection – surface oxide film The main types of aluminum corrosionįor aluminum corrosion the following main types are characteristic :įigure 2 – General corrosion of aluminum: dissolution of natural oxide film It should be emphasized, that the resistance of aluminum and aluminum alloys to normal environmental conditions is very high.
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