High purity aluminium products chemical theory!

High purity aluminium products of electrochemical polishing is the metal anodic dissolution unique electrolytic process, it's being affected by many variable factors influence. According to the nature of the metal anode, electrolyte composition, concentration and process condition is different, in the anode surface may occur in the following one or several reaction: 1) metal oxide into metal ion into to the electrolyte, M = M2 + + 2 e; 2) anode surface generation passivation film, M + H2O = MO + 2 h + + 2 e; 3) gaseous oxygen precipitation, 2 h2o = O2 + 4 h + + 4 e; 4) electrolyte of components in anode surface oxidation. Electrochemical polishing after the anode surface state depends mainly on the above four kind of reaction degree of strength. However, because of the complexity of the electrochemical polishing process, it puts forward all kinds of electrochemical polishing mechanism all has certain limitation.
High purity aluminium products of viscous membrane theory:
By JacguetP A proposed mucosa theory [4] think: when the current through the electrolyte, the anode surface create A layer by anodic oxidation product composition of viscous liquid membrane, it has A higher viscosity and larger resistance, and its thickness in the rough surface of each part is not equal, the thickness of the parts in the sag is greater than the convex parts of the thickness. Due to the anode surface "insulation" different degree, and on the surface of the anode current distribution non-uniform, convex parts of the current more sag parts of the current big. So, convex parts of the dissolved relatively fast, the result will lead to the rough surface is macro polishing. The limitations of this theory is to can't answer electrochemical polishing process if an anode metal passivation oxidation problem, also cannot explain electrochemical polishing process characteristic of anodic polarization problem.
High purity aluminium products passivation film theory:
The theory is that, in the electrochemical polishing process, the anode polarization its surface generation passivation film, only compact passivated film can suppress the surface of crystallography corrosion. Due to the anode surface trunk and sag parts of the passivation degree is different, the convex parts of the large chemical activity, and begin to form passivation film often incomplete is porous, and sag part in more stable passivation status. Therefore, convex parts of passivating film dissolve damage than recess, the result is convex parts corrosion. Such again and again, until a stable dense passivation membrane layer, the electrochemical polishing effect can reach extremum. Though this theory in microscopic polishing won a perfect explanation, but they shouldn't be better explanation electrochemical polishing process.


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