Does Gold Rust or Tarnish? Gold Corrosion Explained

Gold jewelry is often a sign of wealth, and there is a good reason for this. It’s typically very expensive. This is why one might wonder if gold can rust or tarnish.

Pure gold does not rust or tarnish. This is because it is a noble metal and the least reactive of all of the metals. However, most gold manufactured items are not pure gold, so they will often rust and tarnish.

If you want to know more about the rusting and tarnishing processes in gold, read on. You might find some useful information that can help you take care of your gold items.

What Are Rust and Tarnish?

Some people might think that the terms “rust” and “tarnish” are interchangeable, but the truth is that these describe two different chemical processes. They are two different kinds of corrosion.

Rust, which usually has a reddish-brown appearance, is an iron oxide. It’s formed by a chemical reaction between oxygen and iron, typically taking place when there is moisture in the surroundings. This is something that can happen to any metal that contains iron. Since pure gold does not contain iron, as they are two completely different elements, pure gold cannot rust.

Tarnish is a type of corrosion that forms on metals that do not contain iron, such as brass, magnesium, copper, and aluminum. It’s usually a product of oxidation, similar to rust, but it’s not always oxygen that the metal is reacting with; it is often sulfur dioxide.

Unlike rust, tarnish is self-limiting. Only the top few layers of metal react with the surroundings, and this layer of tarnish will seal in and protect the layers underneath from having the same reaction.

Does Gold Rust or Tarnish?

Pure gold does not rust or tarnish. This is because gold is among the least reactive chemical elements in the periodic table; it is considered to be an inert or noble metal. It is not iron, so it cannot rust. It cannot tarnish because it doesn’t react with oxygen. However, this is only pure gold or 24 karat gold.

When considering manufactured gold items, such as jewelry, it is actually very rare to find pieces that are 24 karat gold. Pure gold is too soft and too malleable to be molded into jewelry. It’s actually very easy to make dents in pure gold.

This is why in order to make items such as jewelry, gold is typically alloyed with base metals. Base metals are those that will oxidize when exposed to the air, in contrast with noble metals, which don’t react with oxygen. The combination of gold with another metal will obviously change the properties of the finished metal.

If the manufacturers of the items alloy gold with other noble metals, such as palladium or platinum, the gold will be more resistant to tarnishing. This is the case with white gold. In contrast, if they allow it with copper or another base metal, it will be less resistant to corrosion, as is the case with rose gold.

When you see tarnished gold, it’s not the gold that has actually tarnished. It is the other base metals in the mixture that have been reacting to the sulfur dioxide, oxygen, and moisture in the surroundings.

In the cases where items have a gold finish and base metals underneath, the tarnishing process can happen if the gold finish has pores that expose the base metals. It’s also more likely if there is a scratch in the gold finish.

The higher the karat of a piece of gold, the less likely it will be to tarnish. Tarnishing is typically seen in items that are less than 14 karat gold. In 14 karat gold jewelry, there may be very slow tarnishing, whereas it is almost nonexistent in 18 karats of gold or above.

Even in the lower karat gold jewelry, you will observe much slower tarnishing than you would observe in other metals, such as silver.

Reasons Why Gold Jewelry May Tarnish

As you know, metals other than gold and iron are capable of tarnishing when exposed to air. Typically, tarnishing occurs when the metal reacts with oxygen and sulfur compounds, in addition to moisture. However, there are certain agents in the surroundings that can make the tarnishing process happen more quickly. These include the following:

  • Chemicals, such as deodorant sprays, perfume, or hair sprays.
  • Compounds in storage boxes, such as organic sulfur compounds.
  • Perspiration on the skin of the person in contact with the metal. Since different people have different body chemistries, gold jewelry will usually tarnish more quickly when worn by people who sweat a lot.
  • Vegetables, fruits, and certain spices that can come into contact with these items. Many of these foods contain sulfur compounds and/or are acidic. Examples include onions, pickled items, fruit juices, and spices.
  • Acidic chemical solutions, such as metal cleaning solutions. There might be tiny pores on the surface of metal items that can leach acid and other chemicals to cause local corrosion.

If an item of yours has unexpectedly ended up tarnished, it could be for any of the above reasons.

Things You Can Do to Prevent Tarnishing

Gold items, even the lower karat ones, are generally very expensive. This is why if you can prevent the tarnishing process or at least slow it down, you might be interested in doing so. There are a few things that you can do:

  • Avoid all of the items mentioned above that can tarnish your gold as much as possible. Don’t let your gold come into contact with sulfuric vegetables or chemicals in sprays. Try not to use generic metal cleaners on these items. If you can, try not to let your jewelry come into direct contact with your skin if you know you are going to be sweating a lot.
  • Take off your jewelry when you’re washing your hands. Soap can dull the finish of your gold jewelry. Even though it happens gradually, the soap suds build up and it becomes harder and harder to clean off.
  • Make sure to store your gold jewelry properly. Store it so that different pieces don’t scratch each other since scratches in the finish can make tarnishing more likely. Make sure that any storage containers are clean and don’t contain any organic sulfur compounds. Adding a packet of silica gel would also be a good idea so that there is less moisture in the air for the gold jewelry to interact with.

Treating Tarnished Gold Items

Even though items that contain mixtures of gold and base metals can tarnish, there is some good news. Generally, you can remove tarnishing from these items.

In order to do this, mix a few drops of mild dishwashing liquid that does not contain phosphates with warm water. You can use either your finger or a cotton swab to wipe the tarnished part of the item with this liquid. Make sure you are using something soft, rather than toothpaste or baking soda since these are too abrasive and can damage your item.

Once you’re done, dry off the item with a soft cotton cloth or just let it air dry completely for as long as it takes. Once it’s dry, you can polish it with a soft cloth for extra shine. If this doesn’t work, you can take your item to a jeweler for a thorough cleaning.

Conclusion

Even though gold can’t rust or tarnish, the same can’t be said for any item that contains gold. However, the owners of these items might still have to deal with tarnishing when the gold has been alloyed with other metals. There are certain tips that you can follow to prevent or minimize this; your items should be fine as long as you know how to take care of them.

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