Brass is a beautiful, golden-hued metal that has been used for centuries to create everything from musical instruments to decorative home furnishings. However, brass also has a pesky tendency to tarnish and turn green over time, especially when it is plated with a thin layer of gold or other metal. This green discoloration, known as verdigris, is the result of oxidation and chemical reactions between the brass, oxygen, and other elements.

While a patina can add character, the greenish hue is often considered unsightly on jewelry, fixtures, and other brass items we want to keep looking pristine. The good news is that with proper care and maintenance, it is possible to prevent or minimize the tarnishing process and keep plated brass looking its best.

The Oxidation Process: Why Does Brass Turn Green?

Brass is an alloy composed primarily of copper and zinc. The copper is the main culprit behind the green discoloration. When exposed to moisture and air, the copper undergoes an oxidation reaction, forming a greenish-blue patina layer. This is very similar to the green film that develops on aged copper statues or copper roofs over time.

There are a few key reasons this oxidation reaction occurs:

Exposure to oxygen – The copper in brass reacts with oxygen in the air, resulting in copper oxide. This chemical change happens more quickly when the air is humid or damp.
Contact with carbon dioxide and sulfur – Chemicals like carbon dioxide and hydrogen sulfide in the atmosphere can accelerate the oxidation process. Industrial pollution is a major source of these chemicals.
Effects of weathering – Changes in temperature, wet/dry cycles, and salt exposure from perspiration or seawater can all contribute to the patina formation.
Acids and other chemicals – Exposure to acidic foods, acidic skin secretions, chlorine, ammonia, and other chemicals may hasten the oxidation reaction.

Once formed, the patina layer of copper oxide adheres tightly to the brass and actually acts as a barrier against further corrosion. So the green film is not detrimental to the structural integrity or strength of the brass object. It is simply an aesthetic change. The patina layer will continue to slowly increase in thickness over time with continued exposure to moisture and air pollutants.

Why Does Plated Brass Turn Green Faster Than Solid Brass?

Plated brass refers to a base metal of brass that has been coated with a thin layer of gold, silver, nickel, or other metals through electroplating. The plating gives the brass a different appearance while still benefiting from the strength and durability of brass. However, there is one downside – plated brass tends to turn green faster than unplated, solid brass.

There are two main reasons for this:

The plating is very thin, usually just a few microns thick. This means it can be worn down or damaged more easily, exposing the underlying brass metal. Scratches and wear from use will allow oxygen and moisture to reach the brass and cause oxidation.
Differences in electrochemical potential between the two metals leads to increased corrosion. The brass base has a different electrical potential than the plating metal, which causes an electrochemical reaction when an electrolyte like water or sweat is present. This accelerates the patina formation on the brass beneath the plating.

Where Does the Green Color Come From? Chemical Composition of Verdigris

The distinctive greenish-blue tone that develops on brass surfaces comes from chemicals formed during the oxidation process. The main components of verdigris are copper carbonate and copper chloride, along with traces of other copper compounds:

Copper carbonate – This blue-green mineral called malachite is a major part of patina. It forms when copper reacts with carbon dioxide and water.
Copper chloride – This greenish chemical occurs when copper interacts with hydrochloric acid or chlorine ions. Salts, skin secretions, and household chemicals often provide the chlorine source.
Copper oxides – These black or brown-black compounds, like tenorite and paramelaconite, develop in early stages of oxidation and then react with carbon dioxide to create green patina layers.
Trace elements – Small amounts of other elements like zinc, tin, iron, sulfur, and silica may also get incorporated into the patina layers. Different trace elements can influence the exact coloration.

The interplay of these verdigris ingredients creates the characteristic soft green patinas, ranging from bluish-green to emerald green. Interestingly, the Statue of Liberty’s green hue comes from the patina formed when the copper surface of the statue oxidized over decades of weather exposure.

When Does Brass Start to Turn Green?

For plated brass items, the onset of green discoloration depends heavily on the quality of the plating job. A thick layer of plating, or use of more oxidation-resistant metals like gold or palladium, will withstand tarnishing longer. Electroplated coatings typically range from just 0.175 microns up to 5 microns in thickness. The thinner the plating, the sooner underlying brass will get exposed.

With frequent use and routine environmental exposure, visible signs of tarnish often begin appearing within 1 to 3 years. However, quality pieces cared for properly may retain their original shine for decades without signs of corrosion or verdigris.

On solid brass items, a patina layer starts forming almost immediately upon exposure to air. But it usually takes 5 years or longer for a noticeable greenish tint to develop on regularly handled brass surfaces. On brass left untouched, the green patina may take just 2-3 years to become visible.

Once patina starts accumulating on solid brass, the greenish coating acts as a protective layer and slows down further corrosion. So while the patina continues to gradually thicken, it does so very slowly on an item that is already partially corroded. This is why vintage brass develops a stability in color after decades of exposure and the green tone does not intensify much further.

Factors That Accelerate Oxidation of Plated Brass

Several factors can speed up the oxidation process and cause plated brass items to start turning green sooner:

Exposure to moisture – Wet or humid environments provide the moisture copper needs to react. Bathrooms and outdoor settings pose higher risks. Even handling jewelry with damp hands can contribute to discoloration over time.
Salty conditions – Salt, such as in ocean water or sweat, accelerates corrosion reactions. Saltwater is particularly problematic for plated brass fixtures and jewelry worn during active use or sports.
Contact with skin – Skin oils, cosmetics, and acidic secretions can wear down plating quickly and promote tarnishing. Copper reacts with fatty acids in skin secretions to create copper soaps, which show up as blue-green discoloration.
Abrasions and wear – As plating gets rubbed thin through regular use, the underlying brass gets exposed to oxidation triggers. Using abrasive cleaners also wears down the protective plating.
Chemical exposure – Household cleaners with chlorine, ammonia, and acids can hasten the patina formation, as can contact with certain foods and beverages. Spices, eggs, citrus fruits, vinegar, wine and mustard contain acids that etch plating.
Air pollution – Sulfur and chlorine compounds in industrial emissions accelerate the brass corrosion process, especially in cities and industrial zones.

Tips to Prevent Green Discoloration of Plated Brass Items

While some oxidation is inevitable over time, you can significantly slow down the tarnishing process and keep plated brass looking its best by following these preventative care tips:

Limit exposure to moisture – Avoid wearing plated brass jewelry in the shower, hot tub, or pool. Quickly dry off plated fixtures after sink or shower use. Store plated items in a dry place.
Clean gently – Use a soft cloth to gently wipe plated surfaces. Avoid abrasive scrubbing. For solid brass with patina, don’t disturb the protective coating.
Apply protective coatings – Apply a thin layer of polish or lacquer formulated for plated metals to provide a protective barrier against oxidation and wear.
Remove tarnish carefully – Use a mild metal cleaner specifically for plated brass to gently remove any green tarnish. Avoid chemical dips with harsh acids or bases.
Promptly fix plating scratches – Re-apply plating quickly to any areas where brass shows through to prevent oxidation reactions. Professionally re-plate items with substantial wear.
Avoid chlorine and acids – Prevent plated items from coming into contact with pool water, bleach, acidic foods, etc. that can damage the plating.
Store properly – Keep plated brass pieces in anti-tarnish bags or enclosed containers to limit air and moisture exposure during storage. Silica gel packets help absorb excess moisture.
Take off before physical activities – Remove plated brass jewelry, watches, etc. before showering, exercising, cleaning or engaging in activities that can lead to chemical or mechanical wear.

With proper care and prompt repair of any plating damage, you can enjoy your favorite plated brass pieces for many years before signs of unseemly green tarnish appear!

How to Remove Green Tarnish from Plated Brass

If a plated brass item does develop light green or blue-green discoloration from oxidation, don’t worry! The patina can often be removed and the original shiny surface restored. Here are some effective methods for reversing brass tarnish:

Non-abrasive metal cleaner – Look for a specially formulated brass cleaner at the hardware store or jewelry counter. Apply a small amount to a soft, clean cloth and gently rub the tarnished areas. Avoid rubbing aggressively so as not to harm the plating.
Baking soda and water – Make a paste with 3 parts baking soda to 1 part water. Gently rub onto stained areas using a soft toothbrush or sponge. Rinse thoroughly. Baking soda is a mild alkaline that will help lift oxidation.
Lemon or lime juice – The acidity in citrus juice can dissolve copper compounds in verdigris. Dip a cotton swab in lemon juice and dab onto affected areas. Let it sit briefly before rinsing. Be careful not to leave on too long as acids can damage plating.
Vinegar soak – For solid brass items with heavy patina, not plated ones, soak in undiluted white vinegar for 5-10 minutes. This will dissolve some of the oxidation layer. Rinse and hand dry thoroughly.
Salt and vinegar – Mix equal parts salt and white vinegar to make a paste. Apply to patinated areas, let sit 2-3 minutes, then rinse and dry. The salt acts as a gentle abrasive to lift off oxidation.
Baking soda and aluminum foil – Place a piece of aluminum foil in a bowl with 1 cup hot water and 2 tablespoons baking soda. Place the brass item face down on the foil and let it soak for 15 minutes. The aluminum provides electrons to reduce copper oxide back to copper metal.

Try testing removers in inconspicuous spots first. Be cautious using chemical dips on plated items, as it risks damaging the plating further. And know that removing patina will expose fresh metal and make it more prone to re-oxidation.

When to Avoid Removing Green Patina

While you’ll likely want to clean off tarnish on decorative household brass, some circumstances call for leaving the patina undisturbed:

The patina is a desired look – Sometimes the green patina is prized for its antique weathered appearance on sculptures, hardware, and architectural features. Removing it would diminish vintage character.
The patina has historical value – Items of significance like the Statue of Liberty’s patinated copper exterior or ancient bronze artifacts should not have the patina removed or altered to preserve authenticity.
It provides needed protection – On antique solid brass instruments and other functional items, an undisturbed patina layer prevents further corrosion and deterioration. Removing it can accelerate damage.
It is widespread and stable – Trying to remove heavy, dark patina buildup that has stabilized across the entire surface of an older brass item can be unfeasible and damage the item. Leaving it may be best.
The brass is porous or intricate – Patina trapped in the tiny pores and crevices of etched, engraved, or porous brass can be difficult to remove fully. Attempting to do so risks harming delicate details.

So consider whether patina removal is worth the effort and risks involved. In some cases, the patina may be part of the inherent charm, character, and preservation of the item.

How to Remove Tarnish and Restore Shine to Plated Brass

If your plated brass develops light tarnishing or patina, you can often remove it and restore the original shine. Here are some safe ways to clean and polish tarnished plated brass:

Use brass polish or tarnish remover: Apply a small amount of mild brass polish containing ammonia and scrub gently with a soft cloth. Repeat if needed.
Try a vinegar soak: Soak the brass for 1-2 hours in undiluted white vinegar. Rinse and wipe dry.
Use baking soda and water: Make a paste with baking soda and water. Gently rub onto tarnished areas using a soft cloth or old toothbrush. Rinse.
Lemon and salt: Cut a lemon in half, dip in salt, and use the juice and salt as a gentle abrasive cleaner. Rinse thoroughly.
Aluminum foil technique: Line a bowl with aluminum foil shiny-side up. Fill with hot water and add a tablespoon of salt and baking soda. Place brass item in the bowl for 5-10 minutes.
Avoid abrasive cleaners: Steer clear of any cleaner containing ammonia, bleach, or acid. Scouring pads, steel wool, and rough sponges will scratch plated finishes.

When attempting to remove tarnish, proceed gently and test cleaners on inconspicuous spots first. Removing patina finishes down to the bare brass will require repeated re-polishing to maintain shine. Consider leaving light patinas intact.

Professional Brass Plating Services for Long-Lasting Protection

For valuable brass items, the best way to prevent unsightly oxidation is having the pieces professionally plated by specialists. Electroplating applies a uniform metal coating across the entire surface to effectively seal out moisture and oxygen.

Professional plating offers these advantages:

Thicker, more durable plating – Up to 30 microns or more of protective plating can be applied versus just a few microns with cheap imitation plating.
Highly polished finishes – Plating metals like gold, silver, nickel and chrome can be buffed to a mirror-like luster.
Customizable looks – Different plating options like antique brass, oil-rubbed bronze and more are available.
Added corrosion protection – Reduces need for ongoing polishing and re-application of protective lacquers.
Improved wear resistance – Expert plating holds up better to frequent handling and use without wearing thin.
Longer lasting – Top quality professional plating typically lasts 15-30 years vs. just 2-5 years for low-grade plating.
Environmentally friendly – Modern plating techniques like brush plating reduce use of toxic chemicals compared to old-fashioned dip plating methods.
Restoration services – Professionals can often strip away old flaking plating and restore worn brass items to a like-new finish.

While professional plating has a higher upfront cost, it pays off in the long run with brass that stays bright, shiny and free of patina for decades. For plated brass pieces you want to keep looking pristine as long as possible, contact a reputable plating shop for services and advice.

Conclusion

Inevitably, plated brass will eventually succumb to oxidation and take on that distinctive greenish patina over time with exposure to the elements. But understanding what causes brass to corrode gives you the knowledge to slow down the tarnishing process and prolong the lifespan of plated brass objects. Limiting chemical and moisture contact, gently handling, and properly storing plated items are all effective ways to delay the onset of verdigris. And should any pesky green spots appear, mild cleaning methods can often restore plated brass to its original brilliance. So you can confidently enjoy using and displaying your favorite plated brass pieces for many years to come.