Brass is one of the most popular materials used in interior design, particularly in older buildings. Hardware fixtures, doorknobs, plaques, coat racks and many other details of a home are often crafted in brass. While the metal has a beautiful sheen, it can change over time due to oxidation. While to many people oxidated brass can look unsightly, it is a condition that can be treated.
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What is Oxidation?
Oxidation is a chemical reaction that occurs when brass, a copper alloy, comes into contact with the air. Generally, when brass is first produced it is sealed in a lacquer, but this lacquer wears away over time. With regular use and handling, the brass itself is exposed to the oxygen in the air, and oxidation occurs which results in a tarnish or patina on the surface of the brass that keeps it from looking clean and bright.
While oxidized brass doesn't always look as nice as brass in its original state, the oxidation process allows the brass to create a protective coating or patina on its exterior to prevent further corrosion or damage.
Brass contains a significant amount of the element zinc, and is therefore susceptible to a process known as "dezincification." This occurs when zinc erodes and the copper retains its shape but not its strength, and results in copper crumbling and falling apart. This is particularly problematic when the brass serves a function beyond decoration, such as a pipe, a bolt or some other connective function. Corroded brass that has weakened can be extremely dangerous.
Identifying Corroded vs Oxidized Brass
Generally, brass corrodes when the zinc, copper and tin components of brass alloy are exposed to water. This is a danger for brass pipes, exterior window casings and the hardware on boats. Corrosion in brass is easily identifiable by reddish or pink splotches on the surface of the object. In addition to the impact of water, exposure to mercury and ammonia can also cause brass corrosion.
Oxidation, on the other hand, looks very different. Oxidized brass is typically blackish, green or blue, and hardens like a thick crust over the surface of the brass. This coating typically flakes off and can be removed to reveal the shiny brass surface. Oxidation has no effect on the integrity of the brass the way corrosion does. Some people leave the brass oxidation on for decorative effect, and it is known as a "patina." Sometimes patinas are deliberately applied to create an aged or weathered look.
How to Clean Brass Oxidation
Cleaning brass can be accomplished with household cleaners easily found at Home Depot or other home improvement stores, but it is also possible to clean brass oxidation naturally without the use of chemicals. Make a natural brass cleaner by squeezing the juice from half a lemon into a bowl, and add about a teaspoon of baking soda and stir until mixed. Apply the paste with a soft cloth to the oxidized brass. Once you've worked the paste into the brass, rinse it with water and then immediately dry it thoroughly with a clean towel to avoid additional damage from water exposure.
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- Corrosionpedia: Definition - What does Brass Corrosion mean? Brass corrosion occurs when the components of the brass alloy, such as zinc, copper and tin, corrode when they come in contact with water. Since brass typically contains a significant amount of zinc, it is susceptible "dezincification" or the corrosion of that zinc. The zinc will selectively corrode in the alloy, leaving behind only a weak shell consisting of the remaining copper. Corroded brass that has been "dezincified" can be identified by a splotchy reddish or pink coloring. Brass is susceptible to other forms of corrosion caused by different chemicals, such as ammonia or mercury, that attack the brass causing it to weaken. Corrosionpedia explains Brass Corrosion Brass is an alloy of cooper, zinc and small amounts of tin. The zinc component of brass is easily lost when it comes into contact with water, causing the brass to easily corrode. This occurs when the zinc corrodes, leaving a copper shell remaining, that is generally quite weak. Generally, corrosion resistance decreases and the concentrations of zinc increases in an alloy. To prevent brass corrosion caused by the corrosion of the zinc component, the zinc content can be kept below 15% and small amounts of tin can be added to the alloy. Brass should never be used in raw-water applications since it is so susceptible to corrosion. Brass corrosion can be prevented by using sacrificial anodes that will corrode before the brass itself does. It is also important to vigilantly monitor brass to further prevent corrosion. Share this: Related Terms Corrosion Alloy Zinc (Zn) Copper (Cu) Pipeline Corrosion Zinc Rich Coating 18/8 Stainless Steel Abatement Aboveground Storage Tank (AST) Abradable Coating Related Articles VIDEO: The Basics of Corrosion and Protection VIDEO: The Basics of Corrosion and Protection VIDEO: Cathodic Protection in 2 Minutes Flat VIDEO: Cathodic Protection in 2 Minutes Flat An Introduction to the Galvanic Series: Galvanic Compatibility and Corrosion An Introduction to the Galvanic Series: Galvanic Compatibility and Corrosion What Causes Stress Corrosion Cracking In Pipelines? What Causes Stress Corrosion Cracking In Pipelines? An Intro to Pipeline Corrosion in Seawater An Intro to Pipeline Corrosion in Seawater 21 Types of Pipe Corrosion & Failure 21 Types of Pipe Corrosion & Failure + View More Articles Featured Q&A Where can I find a coating that is chloride and sulfur corrosion-resistant? Why should cathodic protection and a coating be used together to protect against corrosion? Are there CUI concerns for operating temperatures over 350°F? More of your questions answered by our Experts Related Tags CorrosionType of CorrosionMetals CONNECT WITH US FEATURED PARTNERS PPG PMC Graco Inc. Nycote Laboratories Corporation