Determination of material

With electroplating and many other surface coating processes, the central question often arises in advance:

What material is the object to be coated made of?

To answer this important question, we provide you with a few test methods and tricks - after all, you want to know which metal you are dealing with so that you can coat it properly.

General test methods

1) Visual impression - what colour is my object?

Most metals have a silver-grey colour in their pure form. However, there are also alloys that can produce different colour shades depending on their composition. The surface colour can also be changed by natural oxidation or patination.

In physical terms, the visible colour of a material is the combination of the reflected wavelengths of sunlight. For example, if a material mainly reflects green wavelengths and absorbs other wavelengths, it will appear green. Metals that appear grey reflect a large proportion of the visible light, pure copper reflects more in the red-orange colour range, and after oxidation mainly in the green wavelength range (patina). You can find reference points in the following table:

Colour tone	Material
Grey, dull, matt	Tin, Tin casting
Blue-silver, glossy	Zinc
Fark grey, matt	Lead
Grey-silver, matt	Iron, low-alloyed steels
Grey-silver, glossy	Chrome, nickel, stainless steel
White-silver, glossy	Silver, platinum
Yellow-gold, glossy	Gold, brass
Golden-reddish, glossy	Gold alloy with copper content
Brown-reddish, glossy	Copper
Brownish-gold, glossy	Copper alloy, bronze, rose gold

The object can be tested for magnetism using a commercially available magnet. Magnetism is caused by magnetic fields generated by magnets, electric currents, or moving charged particles. These fields exert forces on other magnetic materials or charged particles. The following scenarios are possible with metals:

Strong attraction	Weak attraction	No attraction
Ferromagnetism describes the phenomenon in which materials such as iron or nickel can become permanently magnetic. The magnetic moments of their atoms align in parallel, which creates a strong magnetic field. Even after removing an external magnetic field, the magnetisation remains, which makes ferromagnetic materials special.	Weakened ferromagnetism due to structural modification with nickel or gold additives.	No ferromagnetism in stainless steels: high nickel/chromium content leads to a crystalline structure despite high iron content, which is referred to as austenitic or martensitic steel.
Ferro = Iron, Materials containing iron, low-alloy steels or cast iron, more rarely pure nickel or cobalt, magnetic chrome steel 18/0.	Alloyed stainless steels, weakly nickel-plated objects, nickel-plated and gold-plated objects.	Aluminium, copper, brass, silver, gold, zinc, stainless steels such as austenitic steel V2A and V4A (1.4301 / 1.4404); martensitic steel (1.4021).

Jewellery made of gold, silver and platinum as well as silver cutlery and tin plates are often hallmarked. This means that a symbol or number is stamped into the item with a hallmark, which is used to indicate the degree of purity or the strength of the alloy.

4) Differences due to weight and density

Aluminium and aluminium alloys differ from heavy metals in their low specific weight. Aluminium has a low density of 2.7 grams per cubic centimetre. Iron, on the other hand, has a density of 7.8 grams per cubic centimetre.

Material	Specific weight or density [g/cm³]
Aluminium	2,70
Titanium	4,54
Chrome	7,19
Tin	7,30
Iron	7,87
Stainless steel	8,00 (ca.)
Brass	8,50
Bronze	8,73
Cobalt, Nickel	8,90
Cooper	8,96
Silver	10,49
Gold	19,32
Platinum	21,45
Zinc	7,14

Rust formation in low-alloy steels and iron

Green patina or copper patina oxidation

Black colouring of pure silver

6) Plausibility - which metal do I probably have in front of me?

Certain objects are usually made of the same metal or similarly coated, here is a small selection:

Bathroom tap/water tap:

Taps and sanitary fittings are usually always chrome-plated. Before re-chroming, excess chrome must be removed.

Screws, nails:

(With yellow or bluish colour) Consist of chromated zinc. Chromium(VI) salts are very toxic and are excluded from sale to private customers; our chromium electrolyte contains chromium(III).

Vintage car parts, chrome-plated:

Parts of classic or vintage cars usually have a copper-nickel-chrome layer structure. If they are damaged, they should first be de-chromed, then activated and finally re-plated.

Window handles:
Handles for everyday use are usually made of aluminium or aluminium alloys, which can be coloured green, blue, black or red by anodising or darkened by aluminium burnishing.

Wheel rims:

The rims of new vehicles are almost always made of aluminium because it is matt and lighter. Coating in the bath is not feasible due to the size of the rims and the amount of electrolyte required.

Fashion jewellery:
Fashion jewellery is often made of gold-plated plastic or gold-plated base metal. Before electroplating, a conductive intermediate layer is applied, e.g. copper conductive lacquer or palladium.

The metals at a glance

All the data on the metals is summarised clearly below.

Aluminium

Aluminium is a silver-white, relatively soft and tough light metal. It differs from other metals due to its low weight and from iron and steel due to its non-magnetic properties. It is usually found in various alloys and is somewhat harder than pure aluminium, depending on the application. It is very important in lightweight construction and industry. Possible coating processes: Anodising, burnishing, electroplating (after generating conductivity).

Occurrence: Automotive industry, electronic parts, bicycle parts, electronic housings, window handles or spectacle frames.

Copper/copper alloys:

Red-brownish shiny surface. Non-ferrous metals are alloys of copper with other metals and fine copper. Red gold alloys of copper and gold are used particularly frequently in the jewellery industry. Non-ferrous metals are treated like copper. Copper is a very good electrical and thermal conductor, ductile and, as a pure metal, easily malleable. Oxidation produces a green patina.

Occurrence: Coins, jewellery, handicrafts, electronics, pipes, musical instruments.

Stainless steel

Mostly non-magnetic. Many different types, but with similar behaviour. Very scratch and corrosion resistant, partly acid resistant, depending on composition very hard, ductile and rustproof. 18/0 (18% chromium, 0% nickel, 82% iron): Stainless steel for some cutlery, magnetic 18/10 (18% chrome, 10% nickel, 72% iron): V2A steel, very common, non-magnetic.

Occurrence: Valuable everyday objects, water pipes, tools, pots and household appliances, machines, industry, jewellery.

Iron/steel

Very frequently used. Recognisable by strong magnetism and possible flash rust. Pure iron or low-alloy steel is ferromagnetic and shiny silver-grey. In contrast to alloys and stainless steels, somewhat softer and less scratch-resistant. Iron oxides are black (partly stable oxidation stage II) or reddish-brown (stable oxidation stage III). Pure iron is ductile and mechanically malleable.

Occurrence: Structural steel, historical tools, iron nails, decorative outdoor sculptures, furniture.

Nickel

Nickel is a silver-white, corrosion-resistant metal. Nickel is magnetic and has weak oxidising properties. It is almost never found in its pure form. It is usually alloyed with iron and chromium (V2A steel). Nickel-plated surfaces are rare as they have an allergenic effect. Nickel coatings are usually gold-plated or chrome-plated, as nickel forms an ideal intermediate layer alongside palladium. Strict regulations apply to the sale of nickel and nickel solutions in Germany.

Occurrence: Alloys, e.g. stainless steels and inexpensive jewellery, (intermediate) coatings, nickel coins.

Silver

Shiny white metal, very often patinated (e.g. on coins, jewellery or decorative objects) and then very dark to black. Easily recognisable by the widespread hallmarks (see above), ductile/malleable material, highest thermal conductivity and highest light reflection of all metals, therefore valuable and versatile.

Occurrence: Jewellery, early cutlery and crockery, coins, ingots, nanotechnology.

Chrome and chrome alloys

As a rule, chrome-plated objects have a shiny appearance and a metallic surface reminiscent of a mirror. This effect makes chrome-plated surfaces desirable. Chrome surfaces are usually magnetic because there is iron or nickel under the chrome layer. Chrome has a slightly bluish lustre. Before electroplating, objects must first be dechromed with a chrome remover before they can be activated and then recoated.

Occurrence: Bathroom fittings, sanitary fittings, car, bicycle or motorbike parts, vehicles, cutting tools, medicine, aerospace.

Platinum

Platinum has a silvery-white lustre, is highly corrosion-resistant and has limited resistance to acids. Platinum is very ductile and therefore very malleable. Platinum is very expensive and platinum jewellery can be recognised by its hallmark. Its high density makes it a very resistant material, but it is only used for high-quality jewellery and applications due to its low occurrence and complex processing.

Occurrence: Jewellery, electrodes, catalyst in chemical processes, dentistry, electronics.

Tin

Cast tin is matt, dull and light grey, solder is shiny silver-white. Tin is easily recognisable by its hallmark. Rarely found, very soft material with a low melting point. Tin is known for its ability to form alloys.

Occurrence: Tin plating (corrosion protection), frequently used for historical plates and jugs, pipes, coins, artefacts, ceramics, decorative objects.

Zinc

Zinc is a shiny, silver-bluish metal that is characterised by high corrosion resistance and relatively low hardness. It is an important component of many alloys, such as brass, and is used in various industrial applications. Zinc is softer than many other metals and is characterised by its ability to form oxidations that act as a protective layer. Compared to iron and steel, zinc is not magnetic. Zinc is often found as a galvanised material, where it is applied as a passivation layer on iron or steel to protect them from rust. Possible coating processes for zinc are galvanising and burnishing.

Occurrence: Outdoor installations, railings, buildings, noise protection, facades, halls, vehicles, screws and nails.

Disclaimer

The information provided here is a rough estimate and therefore without guarantee. We do not guarantee the accuracy and completeness of the above information. A binding material analysis cannot be made, at most an estimate of the benefits for electroplating.

Gold:	Common hallmarks are 333, 585, 750 and, more rarely, 900, where the number represents the percentage per 1000 total parts, i.e. 333 gold consists of 33.3% fine gold.
Silver:	The most common hallmarks are 800, 830, 835 or 925 (sterling silver). The alloy component is often copper to make the silver harder, as it is too soft on its own. German silver cutlery is often hallmarked with a crescent and a crown. Silver-plated cutlery usually bears a 90s or 100 hallmark on the back, which indicates the gram weight of a cutlery set of 12 forks and spoons. Silver-plated cutlery is treated like pure silver due to the thickness of the coating. This means that it can be galvanised and polished.
Platinum:	Usually high-alloy 950 platinum.
Tin:	The most common is 950 tin (dinnerware and tin plates), 1000 ‘pure tin’ is quite common. Angel hallmarks are used when there is no lead in the tin, as the colour becomes dull and matt grey as the tin content increases.
Stainless steel:	Stainless steel can be recognised by the hallmarks ‘stainless steel’ and the marking 18/10, 18/10 or 18/0 for the percentage of chrome/nickel in the alloy.