Consequences of over-protection in cathodic protection
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This post was last edited by HITYORKE on 2009-12-28 at 11:46. In a medium-temperature electrolyzer of 3000A, the prepared electrolyte KH2F3 is subjected to electrolysis; fluorine gas is produced at the anode, while hydrogen gas is produced at the cathode. The fluorine gas is used to manufacture fluoride products. Since the electrolyzer is made of carbon steel and suffers from severe corrosion, external current cathodic protection is employed; an electric current is applied to the tank body (a wire connects the tank wall to the cathode) in order to supply the electrons lost by iron during corrosion, thereby achieving protective effects... At present, this protection system does not include any means for monitoring the cathodic protection potential, nor does it have a reference auxiliary electrode – only a wire is connected. Theoretically, that’s how it should work, but I personally think it’s a rather absurd approach ( Embarrassing ); the effectiveness of this protection method still needs to be verified. My question is: if a direct current of 3000A is applied to the electrolyzer, could it cause overprotection of the cell? What would be the consequences of such overprotection?
In fact, the entire tank is used as the cathode, and in practical use this is a very effective measure. Based on our usage, there is no issue of over-protection; rather, under-protection leads to increased corrosion.
With such a large protection area, what material is used for the auxiliary anode and what is its size? An inappropriate design and layout of the auxiliary anode can also lead to insufficient protection in certain areas.
There are two points of confusion in your description: 1. You mentioned photocurrent, but there is no information regarding the sacrificial anode; so what is the purpose of this protection device? 2. The key to the impressed current protection method is to keep the potential of the equipment to be protected (the electrolyzer) below the ambient potential. I’m not sure where the figure of 3000A for direct current comes from Furthermore, excessive protection can easily cause hydrogen embrittlement in the electrolyzer.