What is oxidation of metal labels?
Oxidation is a chemical reaction between the metal and oxygen in the air. On metal labels in tin, copper or brass the shiny surface slowly changes colour, becomes dull or greenish white, this is called discolouration. Aluminium also oxidises, but it instantly forms a protective layer, so it does not discolour further.
Key points
- Tin oxidises the fastest outdoors: after 6–12 months visible dark darkening despite the protective layer
- Copper forms a green patina: a classic beautiful effect, but not always wanted on branded clothing or premium products
- Brass turns duller: subtle but noticeable colour loss, especially visible on dark backgrounds
- Aluminium stays stable for 5+ years: colour does not perceptibly change, even in coastal climates
- Protective layer helps, but is not a full guarantee: tin/copper/brass still oxidise where metal is exposed (for example at damaged edges)
- Printed top layer gives partial protection: where text or colour sits, oxidation is slowed; exposed metal can still discolour
- Material thickness varies a lot: tin 0.16 mm, copper and aluminium 0.10 mm, brass only 0.06 mm, thinner materials are more sensitive to environmental factors
- Lead time 4–5 weeks after approval of digital preview: you have time to choose the right material before production starts
Why does oxidation occur on metal labels?
Your metal label is only 1 mm thin. This thickness consists of the actual metal (0.06–0.16 mm depending on material), a 3D relief, and a self-adhesive layer. On top sits a protective layer (usually clear) that slows oxidation, but does not block it completely. More guides on this topic are in the category Metal labels.
Outdoor exposure to moisture, salt (in coastal climates), and UV light speeds up oxidation. Tin is the most sensitive: after a few months it already forms a dark grey to almost black layer. Copper and brass form more patina and discolouration, shifting from gold to green. Aluminium stays shiny because the oxide layer is microscopically thin and protects the metal underneath.
Aluminium: the reliable choice for outdoor use
In practice we recommend aluminium if you know your label will be outdoors. As a price example, an aluminium label of about 3.5 cm costs around €1.27 per piece at 250 units, the same price as tin. The difference: after 5 years aluminium still looks new, while tin has become dark and dull. All versions and prices are on the page 1 mm metal labels.
Aluminium does not get a visible patina. What can happen: very light, almost invisible greying on much older labels (10+ years) in extremely acidic or salty environments. But for most uses, bike labels and accessories, outdoor tools, garden furniture, aluminium literally stays stable in colour for years.
Tin, copper and brass: when they are suitable
This does not mean you should avoid tin, copper or brass. They each have benefits: tin gives a classic silvery effect with fine details (thanks to the 0.16 mm material thickness), copper and brass give a warm, premium look. They are ideal for indoor applications where the label does not see weather: Read our guide on metal label finish.
- Musical instruments: a guitar is usually indoors, sometimes on stage
- Furniture: a cabinet tag on an indoor cupboard in a living room or office
- Candles and interior labels: labels on candles on the mantel or bedside table
- Premium packaging: a perfume bottle or wine bottle sits in a display, not in the rain
For these cases the protective layer is fully sufficient. Your label stays shiny for years and carries no discolouration risk.
Printed top layer: protection with caveats
Many business owners choose a printed top layer (full colour print on the label). This protects the underlying metal well, as long as the print is complete. You do not see bare metal then, and where metal is exposed (thin edges, corners, small holes), it can still oxidise slightly.
From experience we know this is rarely a problem in practice: protective layer + print layer together work strongly. But be aware: a 100% white print on tin protects only where the ink sits. The edges remain exposed and can still darken outdoors after 1–2 years.
Our advice if in doubt: choose aluminium and forget the oxidation issue. If you really want tin or copper, make sure the print runs to all edges where the label ends, with no exposed metal.
How do you prevent oxidation in practice?
You can do a few things: Read our guide on metal label thickness.
1. Choose the right material for the environment. Outdoors = aluminium. Indoors = free choice (tin is classic, copper warm, brass elegant).
2. Prevention is better than repair. As soon as your label is placed outdoors, oxidation (gently, invisibly) starts right away. You can slow it by applying an extra clear protective spray coat, but that costs time and money, better to choose the right material straight away.
3. Check the position. A label on a surface that faces the rain is more exposed to weather than a label on the inside of a door. Place it as protected as possible.
4. Accept patina on copper as a character trait. Many designers find green copper oxidation beautiful. Entrepreneurs in the craft/vintage sector present this as a feature, not a flaw.
Who needs to think carefully about material selection?
Bicycle manufacturers: aluminium for frame and mudguard
A bicycle frame or mudguard is outdoors all the time, exposed to rain and road salt. You always choose aluminium, and almost always the metal label, not the hard badge. A 1 mm label is flexible and follows the curve of tubes and panels; a rigid 3 mm badge would not bend. Aluminium prevents the label turning dark and dull after a single summer. More background on oxidation can be found on Wikipedia.
Furniture makers: freedom to choose on style
Labels for furniture can be used indoors and outdoors, think garden furniture versus bedroom cabinets. For indoor furniture you can pick tin or brass without worry; for outdoor furniture we advise aluminium. A classic wooden dining table with a brass tag will look perfect for 10 years. The same table outside, under a canopy? Aluminium, otherwise you will see oxidation.
Cosmetics and wine producers: indoor use means peace of mind
Labels for perfume bottles and labels for wine bottles usually sit indoors (shop shelf, display case, wine cabinet). Oxidation does not play a role here, you choose purely on aesthetics. Copper gives warmth, tin gives classic silver, brass gives luxury. Your protective layer + possible print layer are fully sufficient.
Comparison: what to do if oxidation still occurs?
If you see an oxidative film after years: you can gently clean a metal label with a mild cleaner and a microfibre cloth. Note, do not use harsh abrasives that damage the protective layer. For copper you can use a dedicated copper polish; this partly restores the shine. For tin, restoration is harder because it fades again quickly.
Better advice: replace the label. You can remove a metal label later with an adhesive remover (not sharp tools) without leaving glue residue or scratches. Peel it off carefully, rinse away any glue residue, and apply a new label in the same spot.
Schild Inc has placed more than 800,000 labels, here is what we have learned
We have worked since 2021 with more than 1,200 business customers in 19+ countries. Almost 95% order again. What stands out?
- Bicycle manufacturers always choose aluminium for outdoor use; they do not say “oxidation” but “service life”. They want their brand to look the same after 3 years.
- Furniture makers and decorators underestimate outdoor conditions. They choose tin because it looks nice (0.16 mm thickness gives finer details), but then put the label on a garden chair, and the customer calls after a season: “Why has the label turned grey?”
- Cosmetics and food can choose calmly. Their labels sit in packaging or a shop cabinet and almost never see weather or sun. Here design and brand feel dominate, not oxidation resistance.
Our view: oxidation is not a mystery, it is materials science. Know your use case, choose your material. Aluminium costs the same as tin, but gives 5 years of peace. No more indecision.
Practical tip: the role of the adhesive type
The adhesive under your label also plays a role. We use yellow Lohmann adhesive (Germany) for aluminium and tin, and 3M adhesive for copper and brass. These adhesives are chosen because they bond better to these metals and resist moisture and UV better. For very large copper or brass labels we sometimes use a thicker Lohmann adhesive, otherwise surface tension can lift the edges.
The neat detail: the right adhesive is a matter of testing; for every metal + substrate combination Schild tests it in advance. You do not need to figure this out yourself. See our custom metal labels and tell us your use case, we will select adhesive and material based on experience.
Minimum order: choose your material without big risk
A common mistake is choosing tin “because it feels cheaper” and then ordering 100 units. Result: €3–4 per piece, while 250 units are already around €1.27 per piece. You also have no room to switch to aluminium later.
Our advice: for your first order, get 250 units of the material that feels best to you (aluminium, tin, whatever). We give you a free digital preview, so the risk is low. Lead time is 4–5 weeks. Costs less than you think and you gain certainty about material and oxidation behaviour.
Do you really want to test? For new customers we have a test pack of 50 or 100 metal labels, you pay more per piece, but you will see how oxidation behaves in your specific environment (indoors, under a canopy, full sun, salty air).
Bottom line: yes, oxidation is real, and yes, you can prevent it
Oxidation of metal labels is not a production fault or quality issue, it is physical science. Tin, copper and brass oxidise outdoors within 6–24 months. This is not bad, but it happens. Aluminium does not; it stays stable. Indoor use? All materials are fine, oxidation does not play a role.
Your choice is simple: if you know your label will be outdoors, choose aluminium. If you are sure it stays indoors, choose on aesthetics and budget (tin = classic silver, copper = warm, brass = elegant, aluminium = neutral modern). The protective layer does its job; you do not need to feel guilty. And if you do place a tin label outdoors and it oxidises? You remove it painlessly and stick on an aluminium label, no scars or scratches.
