So, does brass rust? Let’s unpack this common question: rust occurs when iron combines with oxygen, brass metals do not contain iron, brass is actually an alloy of Zinc and Copper!
Table of Contents
Understanding Brass: Composition and Properties
- Brass is composed primarily of copper and zinc, typically with a ratio of 66% copper to 34% zinc.
- The proportions of copper to zinc in brass can be adjusted, which in turn changes its characteristics such as color and mechanical properties.
- Brass is known for its golden colour that can shift to a silvery hue with increasing zinc content; it has a density of approximately 8.4 to 8.73 g/cm3 and is appreciated for its malleability.
- Brass behaves as a substitutional alloy, enabling copper and zinc atoms to replace each other within the crystal structure, enhancing its versatility in applications.
Copper-Zinc Alloy
- Brass is primarily composed of a copper-zinc alloy.
- Higher copper content in brass makes it softer and more golden in color.
- Typical brass composition includes about two-thirds copper, one-third zinc, and small amounts of other elements which can influence its corrosion susceptibility.
Corrosion Resistance
- Brass does not contain iron, which is a primary factor in the corrosion resistance of the material.
- The copper component of brass undergoes oxidation, resulting in the formation of a green patina that acts as a protective layer against further corrosion.
Does Brass Rust?
- Rust occurs when iron combines with oxygen in the air, forming iron oxide.
- Brass metals do not contain iron, which is responsible for rust formation.
- Brass is an alloy of zinc and copper and neither of its constituent metals can rust.
Absence of Iron
- Rust formation is a chemical process that specifically involves iron and oxygen, often accelerated by the presence of water or moisture.
- Brass is an alloy consisting primarily of copper and zinc, with no iron content.
- Due to its composition, brass does not undergo the rusting process that plagues iron and iron-containing metals.
Patina Formation
- Copper in brass reacts with sulfur to form a brown and eventually black surface layer of copper sulfide.
- This copper sulfide layer further oxidizes in the air to form a green-blue patina of copper carbonate.
- The patina that forms on brass is not an indicator of damage, unlike rust which signifies metal degradation.
- The patina serves as a protective layer that shields the brass from further corrosion.
Factors Influencing Brass Corrosion
- Brass can corrode when exposed to environmental factors like moisture, chlorides, acetates, ammonia, and certain acids.
- The corrosion process of brass is influenced by the chemistry of the environment, physical wear, and contact with other metals.
- Adjustments to the alloying elements of brass can enhance its resistance to corrosion mechanisms such as dezincification.
- Dezincification resistant brass is produced by either adjusting the zinc content or adding inhibitors like arsenic, nickel, tin, phosphorus, and aluminium.
- The resistance to dezincification in brass parts is also dependent on their manufacturing processes, such as the methods of forging or annealing.
Environmental Conditions
- The rate of brass corrosion escalates under humid conditions due to the combined action of moisture in the air, oxygen, and the metal surface electrons.
- A critical point at 80% relative humidity exists, referred to as critical humidity, where water is neither evaporating nor absorbed, which increases the potential for corrosion.
- Corrosion activity on brass can double with a temperature increase of 50°F (10°C), demonstrating the temperature sensitivity of corrosion rates.
- Environmental chemistry, including pH, oxygen concentration, and ionic strength, affects the kinetic rates at which brass dissolves and hence its corrosion process.
- While regular brass may react with saltwater due to its zinc content, specially formulated marine brass with added tin is better suited to withstand corrosive marine environments.
Alloy Composition
- Naval brass, with a specific composition of 40% zinc and 1% tin, demonstrates improved resistance to zinc leaching and is suited for applications in seawater.
- The use of dezincification-resistant brasses is critical in environments where standard brasses fail to meet corrosion risk standards.
- Dezincification of brass, characterized by the selective leaching of zinc, can be prompted by exposure to water or moisture.
- Environmental conditions such as slightly acidic or alkaline water, low aeration, or higher temperatures can accelerate the dezincification process in brass components.
- Brass alloys can include additives like arsenic, lead, phosphorus, aluminum, manganese, and silicon to enhance their corrosion-resistant properties.
- Corrosion-resistant brass alloys are strategically utilized in areas like water boiler systems and plumbing to prevent long-term failures.
Comparing Brass to Other Metals
- Galvanized steel, coated with a protective layer of zinc, provides enhanced corrosion resistance by acting as a barrier against oxygen and water and forming zinc oxide when scratched.
- Anodized aluminum is very resistant to corrosion which makes it competitive with brass, particularly as it does not tarnish like brass does.
- Stainless steel offers superior corrosion resistance and strength, making it a more costly option than carbon steel and often preferable to brass for certain applications.
Aluminum
- Aluminum does not rust because it lacks iron, which is necessary for rust to form
- When exposed to water, aluminum naturally forms a protective aluminum oxide film that prevents further oxidation
- Aluminum is favored for applications requiring a high strength-to-weight ratio due to its lightweight and malleable nature
Stainless Steel
- The corrosion resistance of stainless steel is primarily due to its high chromium content.
- Chromium in stainless steel reacts with oxygen to form a protective chromium oxide layer on the surface.
- Continuous corrosion resistance of stainless steel is achieved through regular maintenance that allows the reformation of the chromium oxide layer.
- Unlike galvanized steel, which needs a zinc coating for corrosion protection, stainless steel inherently resists corrosion through its chromium content.
Galvanized Steel
- Galvanizing is a method of rust prevention where iron or steel is coated in a thin layer of zinc.
- By applying a zinc coating, galvanization prevents oxygen and water from reaching the steel or iron underneath, which in turn prevents the formation of iron oxide, or rust.
Applications of Brass in Corrosive Environments
- Due to its high corrosion resistance, particularly to saltwater, brass is a preferred material in marine applications such as shipbuilding and underwater equipment.
- Brass is a popular choice for plumbing fixtures, valves, and fittings thanks to its durability and resistance to corrosion.
Marine Applications
- Brass is resistant to corrosion in marine applications due to its unique composition that lacks iron and is capable of handling the harsh conditions of saltwater.
- Brass is commonly alloyed with elements like aluminum for increased strength; tin, which is used in seawater applications to prevent zinc leaching; or lead, to enhance sea-worthy properties such as corrosion resistance.
- In marine environments, brass is employed for various components such as shafting, piping, and creating marine fasteners as well as in motors and pumps, owing to its durability and corrosion resistance.
Plumbing Fixtures
- Brass is a popular choice for plumbing fixtures due to its natural resistance to corrosion.
- Plumbing fixtures made of brass are designed in a range of shapes and sizes to meet diverse plumbing requirements.
Care and Maintenance of Brass Items
- Before cleaning, determine if an item is made of genuine brass or is brass-plated, as the cleaning methods differ.
- Items made of brass that are handled often need more frequent cleaning and polishing to retain their shine
Cleaning and Polishing
- Natural cleaners like a mixture of lemon juice and baking soda can effectively remove buildup from brass items.
- A paste made from flour, salt, and vinegar can be used to eliminate tough stains on brass.
- Tomato sauce, due to the acid in tomatoes, can serve as an easy cleaning agent to remove tarnish from brass.
- Plain white toothpaste can serve as a gentle abrasive to clean and polish brass objects.
- Cleaning brass with a lemon and salt involves using the citric acid in lemon to break the bond of tarnish on brass while the salt acts as a mild abrasive.
- Applying a polyurethane coating after polishing can help keep decorative brass finishes tarnish-free for an extended period.
- To prevent future tarnish and discoloration on brass, commercial brass polishes can leave a protective coating on the surface.
- To avoid damaging lacquered brass items, professional cleaning is recommended rather than using common cleaning methods.
- For lacquered or sealed brass, only dusting or wiping with a damp cloth is recommended to avoid damaging the protective coating.
- A paste made from baking soda and vinegar can be used to polish brass, but it’s important to be gentle and not leave the vinegar on too long as it can dull the metal
Preventing Tarnish and Corrosion
- Minimal handling of brass items is recommended to maintain shine, as skin oils can accelerate tarnishing.
- To preserve brass items, it is beneficial to dust them regularly in order to reduce the effects of air pollutants, which can cause tarnish over time.
- Brass items can corrode when condensation forms on them due to temperature changes; thus, proper storage that minimizes exposure to fluctuating temperatures can help prevent corrosion.
Cleanco Commercial Cleaning’s Approach
With over a decade of experience in the commercial cleaning industry, we are often presented with various brass items, decor and componentry within each of the sites we service. It is widely used in settings such as medical centres, childcare centres, Industrial and people’s homes.
Contact Cleanco Commercial Cleaning today!