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Old July 20th 20, 10:11 AM posted to rec.audio.high-end
Paul Hunting
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Default Do RCA plugs/sockets have a galvanic corrosion problem?

I couldn’t understand why the sound i was getting deteriorated over about a three to six month period. In the end i decided that this might be due to Galvanic or bimetallic corrosion.

This type of corrosion is an electrical and chemical process whereby a metal corrodes when in contact with a different metal. Three conditions need to be met for the process of galvanic corrosion to occur. one there must be two dissimilar metals; further that there is an electrical current flow between them and finally that there is conductive fluid present between them. The initial reaction is to say that this third condition is not met in RCA hookups. However RCA interconnect plugs and sockets are hardly a perfect fit and interconnect contacts will be coated with miniscule amounts of water. Water is a conductive fluid and is present in varying amounts in the air as water vapour. Hence the conditions of galvanic corrosion are met where the plug and socket plating metal is different. This type of corrosion will be more likely in humid and salty climates. Somewhere like Las Vegas has a low humidity and will likely be a low corrosion spot while San Francisco has relatively high humidity and will have higher incidence of mating corrosion..

The following table gives a measure of likely galvanic corrosion of four popular interconnect plug/socket metals. A high galvanic value is about +/- 4 and the lowest is zero. Values under +/-0.3 are considered not significant.

Silver Gold Copper Nickel
Silver 0.0 -0.7 -0.46 -1.05
Gold 0.7 0.0 -1.16 -1.75
Copper 0.46 1.16 0.0 -0.59
Nickel 1.05 1.75 0.59 0.0
Source: Dissimilar Metals And The Risk of Galvanic Corrosion in Mating Connectors
July 23, 2015 By Danny Boesing

The larger the value the larger the likelihood of corrosion. So the worst case for corrosion here is using a gold RCA plug connector on a nickel socket (1.75) or vice versa. While having a silver plug on a copper socket is the lowest (0.46). I surmise that the period over which the process takes will depend largely on local humidity conditions, the level of current, how often the plugs are plugged and unplugged and there maybe other factors. Someone in a low humid climate might have a very different experience of corrosion and its impact on sound compared to someone living in a high humid location. While plugging and unplugging might scrape away the corrosion.

It is true some metals can better withstand corrosion than others. Nickel, silver and gold are supposed to withstand corrosion quite well. Again maybe what we are talking about is over what time period and in what water vapour conditions. And further what we’re really interested here is the impact of corrosion on sound and an answer to the question: how much corrosion needs to occur to impact on sound?

The corrosion happens slowly to begin with, and is not visible to the naked eye. I find that i’m just listening and then suddenly one day it dawns on me that it’s all a bit rubbish and that the sound has deteriorated. What’s needed - new tweeters? new interconnects? a new player? Corrosion results in distortion. The treble balance is awry, there’s a noticeable and annoying ringing or hardness in the upper octave mainly heard with solo piano recordings and other parts of the frequency are affected. It just doesn’t hang together any more. There is an improvement after a contact clean. That gives you another 3 or so months.

What’s the answer? Use amounts of deoxidizing solution. I’m not sure how long these solutions work for. I have just started experimenting with this on an op amp fitted into a plated (gold or copper) socket. You coat surfaces with the deoxidizing solution and it should work and stop the corrosion whatever the corrosion source. I’m wondering if contact grease or lubricant, like electrolube, will have a similar effect. Surely contact grease would keep water vapour out. I have not tried this though.

An alternative solution is to choose connectors with similar plating materials. This should be easy to do if you DIY your own cables. It just means matching nickel plugs to nickel sockets, gold plugs to gold sockets and so on.. And depending on your system you might end up with interconnects with nickel plugs on one end and gold plated plugs on the other. The point being galvanic corrosion only happens with bimetal contact present once you take this out of the equation galvanic corrosion doesn’t occur. I suppose a difficulty with this approach is that you need to successfully identify the plating metal of the socket connector. For instance some coppers can be mistaken for gold. And so called Nickel sockets could be a combination of metals. And the process is upset when plug connectors are say rhodium plated, silver is sometimes rhodium plated to stop it tarnishing, unless of course you have rhodium plated sockets as well.

I did change all my connectors so that each plug and socket had similar, as far as i could tell, plating materials. And there has been no deterioration in sound so far. And, for some of the cables, that was over 6 months ago. So for me this seems to be the solution. it was a leap of faith the first time i fitted a nickel plated plug - i mean they’re so cheap that they did not inspire a lot of confidence. But it worked fine and sounded good.

So do RCA plugs/sockets have a galvanic corrosion problem? I believe so though part of me is not convinced about the conclusion as surely someone somewhere would have spotted this earlier. Galvanic corrosion is a type of oxidation and comes under the general heading of oxidation which has many interconnect and cable references. i suppose, also, there might not be a lot of interest in this. after all corrosion is corrosion, whatever the source. Does it really matter about the source of corrosion? There is also electrolytic (non-contact) corrosion. Galvanic corrosion can be described as a contact corrosion between dissimilar metals and also as a special type of electrolytic corrosion. I’m not sure how you would tell the difference between the types of corrosion. Perhaps galvanic corrosion happens at a faster rate than oxidation because of the presence of current and bimetal contact though water vapour is present for both.

has anyone found similar in their set up? and what do you do about it?
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