How quickly does copper rust and what to do about it
Copper products have been used by people for many centuries ... Even in ancient times, the cost of such a metal could be equal to the cost of gold, since the production of this metal was very expensive.
At the moment, copper has become much cheaper, and therefore, in addition to jewelry, they try to make dishes, accessories for the interior and other items from it.
Have you ever thought about how quickly copper rusts?
Corrosion of copper, unlike the same iron, develops extremely slowly due to its resistance to such a phenomenon, and yet sometimes it is required to take measures to cleanse products from terrible plaque.
Rusting means the process of metal destruction under the influence of negative factors in the environment. To one degree or another, all metals and alloys will rust, and as a result, rust and places of deterioration of integrity (namely, holes) appear on them. Over time, all non-metals can begin to deteriorate - an example is the aging of rubber or even plastic from exposure to oxygen, with constant contact with water, and also due to temperature extremes.
The main root cause of rusting can be considered the thermodynamic instability of the metal to the effects of physical factors or even substances of chemical origin, which are in the contact medium.
In comparison with iron, copper will oxidize much less, but with an increase in temperature, this process will be greatly accelerated. With a regular presence in an environment at temperatures above +105 degrees, any metal will rust several times faster.
Copper is a metal with high ductility properties, which have reddish-golden color, and slightly pinkish after removing the oxide film. In terms of electrical conductivity, it will be second only to silver, and it is also characterized by a huge degree of thermal conductivity. Due to its low resistivity, copper is used in electrical engineering - it is used to make copper plates, windings of electric motors, and wire.
Please note that due to the excellent anti-corrosion properties, the metal will be included in alloys to improve their engineering characteristics (brass, bronze, etc.). In a galvanic environment, copper turns into a cathode, and begins to enter into electrochemical processes, and also causes an accelerated process of rusting of other metals.
Copper is an inactive chemical element, and therefore it practically does not interact with water (sea or fresh), air. If the air is dry, an oxide film with a thickness of up to 50 mn will form on the surface of the material.
A copper product begins to darken, turns greenish or brown, and this is called a patina. In many cases, the patina is perceived as a decorative type of coating.Corrosion intensity is low when in contact with diluted hydrochloric acid, but when reacting with many other acids, with halogens, "aqua regia", the metal will be oxidized to form copper carbonate.
Despite the resistance to damage, even copper products under certain conditions are capable of rusting. Such phenomena are least pronounced in water, humid air, soil, and even more in an acidic type environment.
Corrosion can be significantly reduced by tinning - coating the copper with a tin layer. A high-quality tinning process provides reliability and protection against defects, and also increases resistance to corrosion, makes the material immune to high temperatures, hail, rain and snow. The term of application of tinned products will be more than a hundred years without losing their original qualities.
Copper protection against corrosion is very important. The rate of rusting of copper in water will strongly depend on the presence of an oxide-type film on its surface, as well as on the level of saturation of water through oxygen.
The more oxygen in the water, the more intensive the destruction of the material will proceed. In general, copper can be considered resistant to the harmful effects of fresh and salt water, and only dissolved chlorine ions, and even a low pH, negatively affect it. Durability, as well as resistance to rusting, makes it possible to use materials for the manufacture of the pipeline.
Note that if a green or even brown oxide crust has a green or even brown oxide crust on the surface of a copper-plated product, little destructive components will penetrate inside. As a rule, the oxide layer forms after 2 months of the metal being in water.
Much stronger will be considered a green crust (that is, carbonate), loose and not so strong - black (sulfate).
In sea water, the degree of corrosion is almost the same as in ordinary water, that is, fresh. Only when the movement of water accelerates will rusting become shock, and therefore more intense. Copper is a material that cannot be overgrown by marine microscopic organisms, because its ions are harmful to algae and shellfish. This property of metal is used in shipping, as well as in fisheries.
Copper will not deteriorate in alkalis, because the material itself is alkaline, but acids for it will be the most negative in terms of their effect. The fastest and most significant corrosion will occur when it comes into contact with sulfur and its acidic types of compounds, and nitric acid is capable of completely destroying the structure of the material. Copper begins to dissolve in concentrated acid, and therefore additional protection is required in the manufacture of equipment for the oil and gas industry.
For this purpose, inhibitors are used - retarders of a chemical reaction:
- Shielding - they create a film that prevents acids from reaching the copper surface.
- Oxidizing - help to turn the top layer into oxide, which will begin to react with acids without harm directly to the metal itself.
- Cathodic - increase the cathodic overvoltage, which will slow down the reaction.
Let's look at something else about corrosion
The soil is home to a large number of microscopic organisms that are capable of producing hydrogen sulfide, since the environment is acidic, and the rate of copper corrosion will increase. The greater the deviation of the pH value in the direction of oxidation, the sooner destructive processes will proceed. If the soil is equipped with oxygen, then the metal begins to oxidize, but it will rust less. With a long-term presence of copper products in the ground, they begin to turn green, become friable and can even crumble.
Short-term exposure to soil will create a patina that can be removed from the object. By the way, humid air can have a bad effect on the state of the material only with prolonged contact, and for a start it also causes the formation of a patina (oxide layer). An exception will be steam, which is saturated with sulfides, chlorides, carbon dioxide - corrosion will develop in it more rapidly.
Copper ladles, Turks, samovars have a high degree of thermal conductivity, and therefore heating in them proceeds evenly, and the products will be cooked faster. This is due to the high popularity of products in everyday life.
The need for cleaning copper objects is due to the loss of their visual appeal over time. Products that are exposed to air or even frequently heated up begin to fade and lose their natural color especially quickly.
Copper corrosion in the form of an oxide film (patina) is popular only at a time when it is required to give objects a vintage look, antique stylization. Otherwise, it will deteriorate the appearance of dishes, utensils, as well as figurines and jewelry. To remove oxide deposits, darkening elements and return the previous shine, it is required to clean items from time to time.
Also, purification is required in order to exclude the ingestion of harmful compounds that are present in the green and black layers.
It is not difficult to clean copper objects, it does not require expensive means. Here are the most popular home remedies:
this method works best for items that are only slightly tarnished.
Now let's look at how to clean copper coins.
Copper coins are antiques and will not be produced in our time.
They often need to be cleaned to regain their beautiful appearance. If a copper coin has been in contact with lead, the coating will appear yellowish. In this case, it will be perfectly cleaned with table vinegar (9%). Green plaque should be removed with a citric acid solution (10%) or even natural lemon juice, brown ammonia or ammonium carbonate.
It should be remembered that sometimes the patina layer helps to give coins a more vintage and noble appearance, and therefore it is not always worth removing it.
Some de try to artificially age money with a home method. To do this, take a liter of distilled water, 5 grams of potassium permanganate (pharmacy) and 50 grams of copper sulfate. The solution should be heated without boiling, throw coins into it, leave until the desired shade is obtained. To consolidate the effect obtained, dry money treat everything with a mixture of alcohol and benzene (1 to 1). After the coins take on a beautiful aged look and are able to decorate any collection of antiques.
( 1 grade, average 5 of 5 )
Posted By: Work Style |10, Nov 2020
Posted By: Work Style |06, Nov 2020
Posted By: Work Style |10, Nov 2020
Posted By: Work Style |02, Nov 2020
Posted By: Work Style |11, Nov 2020