A very crucial question in the electroplating field is: “What do I have here in front of me? Which material is the object made of?”
If you’re not sure which material the object you want to plate is made of, we offer you some useful tips for material determination on this page.
1.) General testing methods
1.1.) Magnetic test
A simple test can be realized with a current weak magnet.
A) Magnetic material - Magnet sticks to the object / is strongly attracted
When the material is strongly attracted by the magnet, it is a ferruginous material like low-alloyed steel and less often magnetic chromium steel 18/0 (e.g. used for anti-allergenic cutlery). In rare cases, it could be even pure nickel or cobalt (very rare).
B) Magnetic material - Magnet doesn’t stick tot he object / is weakly attracted
In this case, it may be a weakly nickel-plated object or alloyed stainless steels. Gilded objects often have a nickel priming, which makes the objects weakly magnetic.
C) Non-magnetic material - Magnet is not attracted at all
Under these circumstances, it could be a V2A or V4A stainless steel. With the exception of some kinds of stainless steel, the presence of nickel, iron or cobalt can be excluded almost certainly. Every other material can be possible.
1.2.) Visual impression
The most metallic surfaces in their pure state have a silver-grey shade, with the exception of some metals like gold, copper and its alloys. The gold alloys have a red shade – increasing with its copper content. An example of the so-called Krügerrand gold coin with a gold content of 917 and a copper content of 83 pieces.
Non-ferrous heavy metals consist of copper and copper alloys like, for instance, bronze and brass. Whereas bronze shows a brown-golden shade, most brass alloys have a strong yellowish colour.
Zinc is mostly chrome-plated and then looks like brass (e.g. screws or …). Unlike brass, these objects iridescence, i.e. when in light, there will be rainbow colours on the object, comparable to oil films on water. It exists also blue chromate zinc which also iridescences. The chromatation has to be removed before plating (e.g. diluted hydrochloric acid).
Jewellery made of gold, silver and platinum, as well as silver cuttlery and tin plates are often hallmarked. That means that a symbol or a number is punched into the object with a hallmark:
Gold: frequent hallmarks are 333, 585, 750 and less often 900. These hallmarks indicate the gold content. 333 gold e.g. consist of
33.3% gold and 66.7% alloy metal (mostly copper and silver).
Silver: 800, 830, 835 and 925 (sterling) are common. These hallmarks indicate the silver content (analogous to gold, see above). Silver is mostly alloyed with copper and serves for hardening the very soft silver. German silver cuttlery made of massive silver additionally have a crescent and a crown punched on them. Silver-plated cuttlery mostly have 90 or 100 on their backside. That means that a set (12 forks and 12 spoons) contain 90 / 100 g of silver layer. Silver-plated cuttlery can be treated like pure silver, as the silver layer is relatively thick (< 20 µm). Silver and silver alloys can be plated like pure silver.
Platinum: normally 950 (95% platinum content)
Tin: Tin objects are hallmarked with an angel, when it doesn’t contain lead. Additionally, the tin content is often indicated, e.g. 95% tin or “pure tin” wicht 100% tin content. The most frequent is 95% tin for dinner service and tin plates. If the tin is rather dull grey and doesn’t have any hallmark besides the angel, there is mostly a lot of zinc in it.
All of the hallmarks are to be treated with caution, as they can be falsified! False hallmarks are often detected because they are engraved instead of stamped. This makes the edge of the hallmark less embossed.
Further information about precious metal testing can be found on: www.gold-analytix.de
1.4.) Weight or density
Aluminium and its alloys can easily be distinguished because of their low specific weight. Aluminium has a low density of 2.7g per cubic centimetre. That means that an iron object of the same size is about 3 times heavier. The same applies for copper, lead, silver and many other metals with a similar density to the one of iron. Gilded and silver-plated aluminium can also be easily detected because of its low weight.
1.5.) Oxidation and tarnish colours
Objects that got old can often be discovered by looking at its tarnish colours. Flash rust and rusty spots aren’t formed on stainless steel like V2A or 18/0 chromium steel under normal conditions. Then it is low-alloyed steel or more rarely pure iron. They are however to be treated the same.
A blue or green colouring on brass or golden objects shows the presence of copper (typical for brass or bronze that got old). 333 gold also can tarnish. 585 gold can’t thanks to its high gold content.
After a short time exposed to air, silver is covered with a black patina which smells like addled eggs or musty. These are sulphur compounds from the air that have to be removed with the silver cleaner before plating.
Chrome is persistant and has no patina.
Certain objects are normally plated with the same metal or in a similar way. Please look at the following overview:
Bathroom fittings: these are normally always chrome-plated – the base material has therefore to be chrome
Screws, nails (yellowish of blueish): chromated zinc. Has to be removed before plating (hydrochloric acid), then tob e plated with iron
Vintage car parts, chrome-plated: these mostly have the usual layer-assembly copper-nickel-chrome. According to the damage, it has to be copper-plated (strong damage) or only nickel-plated and chrome-plated
Window handles: mostly aluminium or aluminium alloys
Rims: mostly aluminium or stainless steel
2.) Table of metals and their identification
Aluminium is a silver-white light metal and is relatively soft and tough. Thanks to its low weight, it can easily be distinguished from other metals. It is non-magnetic and is therefore easily distinguishable from iron or steel. It normally comes in form of different alloys and is then somewhat harder than pure aluminium. It is often used, e.g. for bike components, construction designs, window handles or beverage cans.
Nowadays, lead is rarely found and is a toxic heavy metal. It is detectable by its easy ductility and its dark grey colour (rather dull, not bright).
Non-ferrous heavy metals and copper, also nickel silver (Cu/Ni/Zn)
These cases are alloys of copper with other metals and pure copper. Especially frequently used in the jewellery industry are red gold alloys made of copper and gold. The non-ferrous heavy metals are to be treated like copper. Nickel silver is colourless and similar to silver, but behaves like a non-ferrous heavy metal (used e.g. as a base metal for silver-plated cuttlery).
Mostly not magnetic. Many different types that behave in a similar way.
18/0 (18% chrome, 0% nickel, 82% iron): Stainless steel for some cuttlery, magnetic
18/10 (18% chrome, 10% nickel, 72% iron): V2A steel, very frequent, not magnetic
Iron and low-alloyed steel (e.g. construction steel)
Very frequently used. Recognizable by its strong magnetism and by flash rust.
This is a white, corrosion resistant metal. Nickel is magnetic and can’t almost never be found in pure state. It is mostly alloyed with iron and chrome (V2A steel). Nickel-plated surfaces are rarely found because they are allergenic. Nickel layers are mostly gilded or chrome-plated.
Bright white metal, very often patinated and then completely dark to black. Easy to distinguish by the mostly used hallmarks (see above).
These objects normally are very bright and have a metallic surface that almost reminds of a mirror. They are mostly magnetic because of the iron or nickel underneath the chrome layer. Chrome has a light bluish cold gleam. It is often used for bathroom fittings and car- or motorbike parts. It is to be treated like pure chrome.
Bright grey metal. Easily recognizable by its hallmark. Often used for jugs and plates.
Bright grey metal. Very frequently used, as it protects iron from oxidation. Screws, nails, street lights, etc. are therefore mostly covered with zinc. Hot-dip galvanised iron also has a honeycomb-like structure which makes it easy to identify. Small galvanized parts are often yellow chromate and then look similar to brass. In order to electroplate it is advisable to remove the chromatation of galvanised objects with diluted hydrochloric acid and to remove the zinc. After that, it can be treated like iron.