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If you folded up a piece of aluminum foil and put it between the nickel plated terminal of a AA battery and the nickel plated contact in the battery holder....

Would galvanic corrosion cause either the battery or contact materials to become damaged?

Does it matter whether you put the aluminum foil on the positive or negative end of the battery?

Are there any other risks such as safety risks, exploded batteries, or as I've mentioned, any expected corrosive effect that might ruin your device contacts after a period of time?

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    \$\begingroup\$ no safety risks and some cheap batteries are slightly undersized, so a foil shim is suitable for low currents. It may oxidize and need to be adjusted once. No dry cells are safe from leakage after being used for a long time. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Sep 15 '18 at 16:04
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    \$\begingroup\$ @YoeyYutch As a general rule, you should not electrically connect dissimilar metals, except in the case of cathodic protection, or in cases where a product like deox is used to protect the metals, such as when running a copper cable into an aluminum lug. You can look up the anodic index of a material and use that to determine if it is acceptable to bond with another material, in your case, AI=0.65V for tin plating and AI=0.75 for aluminum. The value should be within 0.15V for harsh environments, 0.25V for normal environments and within 0.5V for controlled environments. \$\endgroup\$ – K H Sep 15 '18 at 20:00
  • \$\begingroup\$ @KH Very good comment +1. Battery terminals are sometimes tin but more often (as in the question) they are nickel with an AI of 0.30. BTW, you do not need to reference the OP in any comment (question or answer) and when commenting on an answer you need not reference the author of an answer. \$\endgroup\$ – Misunderstood Sep 15 '18 at 20:48
  • \$\begingroup\$ @Misunderstood Whoops, nice save! I must have seen "Tin" and thought "Nickel" because of the word plating. \$\endgroup\$ – K H Sep 16 '18 at 0:19
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    \$\begingroup\$ @Misunderstood no I think I made the mistake the other way round on the chart I found because I remember seeing "tin plating" and "plating" felt right. Makes no difference though =) \$\endgroup\$ – K H Sep 16 '18 at 1:39
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The battery will be fine.

Would galvanic corrosion cause either the battery or contact materials to become damaged?

While galvanic corrosion is possible between aluminum and nickel (or nickel and any other metal), in most environments, it is not a problem.

Yes, it is possible, but it would depend on the life of the battery (e.g. replaced monthly, yearly, or decennially), the environmental moisture content (e.g. air humidity) and the galvanic component potential.

Humid air is the most likely electrolyte.

If the humidity were 100% then the following may apply (submersed in tap water).

Aluminum has a galvanic component potential of about -375
Nickel has a galvanic component potential of about -125
The difference between the two is only 250.
The difference between the two in sea water is about 450.

So it depends upon the environment. For example if it were used at the beach (with high salt and humidity) would be slightly (insignificant) worse than in an air conditioned office.

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Source: THE EFFECT OF ELECTROLESS NICKEL COATINGS

Does it matter whether you put the aluminum foil on the positive or negative end of the battery?

Good question. I do not believe that current flow has any effect on galvanic corrosion. I have never see this said in any papers I have read on this topic. Intuitively it would sound reasonable the current would exacerbate the corrosion. But I have not seen any papers written proving this to be true. I first learned about galvanic corrosion back in 1972 about joining copper and iron water pipe when I was doing plumbing. Joining copper an iron requires a fitting called a dielectric union.

There are three things necessary for galvanic corrosion. Current flow is not one of them.

  1. Electrochemically dissimilar metals must be present e.g. iron and copper
  2. These metals must be in electrical contact, like pipes screwed together
  3. The metals must be exposed to an electrolyte, like water in the pipe.
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  • \$\begingroup\$ I think the placement question has more "where it can do more harm" meaning. In which case placing the foil at positive end makes it closer to both positive and negative (cell can) terminals, as well as to the most probable point of electrolyte leak. Definitely should be on negative. \$\endgroup\$ – Maple Sep 16 '18 at 4:26
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Without an electrolyte, there would be no galvanic corrosion. Say you're in a very salt water environment, then the aluminum foil will corrode before the nickel does. Aluminum is less noble and will become the cathode on the galvanic corrosion process. Even humid air near the sea can do this. The drier and enclosed the metals are, the less likely it happens. Google "lasagna cell" for examples.

There is zero chance of explosion.

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  • \$\begingroup\$ Thank you for the edit on rust , I removed my down vote. I still feel strongly that galvanic cell is much more informational and relevant than lasagna. But not so strong I could retain the down vote. \$\endgroup\$ – Misunderstood Sep 16 '18 at 3:32
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    \$\begingroup\$ Thank you for your answer. Instead of saying "exploded batteries" in my question I should have said "leaking batteries", but after reading through everyone's comments and answers I feel pretty comfortable about shimming the battery in my VR controllers, which I did today and it worked great! \$\endgroup\$ – YoeyYutch Sep 16 '18 at 3:51
  • \$\begingroup\$ @yoey it wouldn't cause it to leak any more than your environment would \$\endgroup\$ – Passerby Sep 16 '18 at 4:16
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@Misunderstood did a nice job explaining if corrosion can occur. This answer explains the consequences of where the corrosion occurs.

The outside of a typical AA battery is a steel can, positive and negative terminals, and seals between them to keep the liquid electrolyte inside. (The may also be a printed label, which is not important here.) Normally when we think of battery corrosion, it occurs inside of the cell. It attacks the seals, which causes the electrolyte to leak out. In turn, the electrolyte can corrode the outside of that cell, nearby cells, the battery holder contacts, and the circuits of the device itself. Yuck.

With an aluminum foil shim, the corrosion will occur on the foil itself, and any terminals or contacts the foil touches. It will not attack the seals, so it is no more likely to cause the cell to leak. It will increase the resistance of the battery (i.e. like an additional Thevenin series resistance), quite similar to using that device with dirty battery terminals. The amount of corrosion will be quite small, although it will increase with use of the device, so you may not even notice any change in the performance of the device. You can fix it by cleaning the contacts and replacing the battery and foil.

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