Industrial Silver plating has been used for flatware, vases, and candlesticks since the 18th century to give a cheaper alternative to genuine silver. Since the invention of electroplating in the 19th century, industrial silver plating has been ubiquitous. An electric current is passed between two electrodes that are submerged in a silver-based electrolyte solution during plating. One of the electrodes is the substrate, which is the metal or alloy to be plated.
Metal atoms are deposited in a thin layer on one of the electrodes when electricity passes between the two electrodes. Continuous reel-to-reel strip plating and overall and selective barrel and rack plating are all industrial silver plating techniques. It may be done on various materials, including steel, stainless steel alloys, copper, bronze, and aluminium. After plating, a substrate has a dull, matt, or semi-bright appearance.
Why are metals plated with silver?
Industrial Silver plating has various characteristics that make it perfect for current technological applications, including aircraft, telecommunications, electronics, and computer components. The following are some of the advantages of silver plating:
- A surface that is both corrosion and oxidation resistant.
- Exceptional wear resistance
- Improves the substrate’s solderability.
- Even at high temperatures, the lubricity is exceptional.
- Electrical conductivity is high.
- Low-friction characteristics make it anti-galling.
Silver plating can also be utilised in radiation shielding and to increase paint adherence and infrared reflectance.
The benefits of industrial silver plating
There are numerous advantages to silver plating. This sort of coating provides exceptional corrosion resistance to the base material and the product as a whole due to the strength of silver. Silver plating not only provides good solderability for tiny components such as kitchen utensils, but it also has low electrical resistance, making it ideal for any product that requires a high level of polish and conductivity. A silver coating is also beneficial to the product’s lubricity. Unfortunately, silver-finished goods can still tarnish, but silver plating is a more affordable alternative to gold plating, producing similar effects. Overall, the silver coating is utilised on items that need to:
- Resistance to corrosion
- Resistance to wear
The thickness of the silver coating varies depending on the type of use of the coated item.
The uses of industrial silver plating
When compared to all other plated metals, silver has the most significant uses across sectors. As a result, silver plating is a must-have procedure. This is due to the fact that silver is the least expensive of all precious metals. Silver is incredibly inexpensive when compared to palladium and gold. As a result, silver plating is widely utilised in a variety of sectors and for a variety of popular goods, including:
- Bearings, semiconductors, and connections are all examples of electronic components.
- Batteries and solar panels are examples of power generators.
- Various musical instruments
Silver plating is a common and frequently utilised quality plating method in a variety of industries. Its strong conductivity, excellent solderability, and corrosion resistance make it extremely valuable, especially considering its affordability and gold comparison.
Plating and surface coating technologies in other forms
Although silver is a good coating for many substrates, different coatings may be utilised to satisfy various technical criteria for hardness, corrosion resistance, and low friction. Gold, brilliant tin, matt tin, nickel, and copper are examples of coatings that improve electrical characteristics and solderability. Other surface coating methods include hard anodised coatings, sulfuric anodised coatings, PTFE impregnated anodised coatings, electroless nickel coatings, and nickel boron coatings, in addition to the plating.
Durability, wear and corrosion resistance, low-friction and anti-galling resistance, chemical resistance, and hardness are all characteristics of each. Aerospace, defence, electronics, semiconductor, and automotive industries profit from surface coating services’ technical developments.
The process of industrial silver plating
Alkaline cyanide solutions are used for almost all industrial silver plating. Non-cyanide substitutes have been the subject of a great deal of study. Some iodide, trimetaphosphate, thiosulfate, and succinimide-based systems have been discovered to function. Silver cyanide salt, alkali cyanide, alkali carbonate, alkali hydroxide, and, optionally, brighteners make up the silver bath. The use of sodium salts is possible, although they are less conductive than potassium salts, resulting in lower current densities. Because sodium salts might cause some yellowing of the coating, the most commonly used compounds are potassium salts. The silver is generally added as potassium silver cyanide KAg(CN)2, with a typical silver metal concentration of 10–40 g l1 in solution (37,39).
With cyanide, silver produces complexes. The complexes’ dissociation constant is extremely low, lowering the electrode potential significantly. There are just a few free silver ions in the solution, and cyanide complexes cause deposition. Aside from increasing conductivity, alkali cyanide is supplied to the bath to maintain a high enough cyanide level for anode dissolution and to compensate for losses produced by dissociation reactions with oxygen and carbon dioxide in the air. Depending on the salts employed, potassium or sodium cyanide is utilised.
Alkali carbonates improve the conductivity of the bath and its throwing power. The coating will be harsh if there is too much carbonate present. The excess sodium carbonate in the solution may be frozen out, but the greater solubility of potassium carbonate prevents this. Although barium cyanide may be used for precipitation, it is impracticable; thus, potassium baths are generally replaced when the amount of carbonate is too large. Other contaminants will be removed as well.
The silver bath’s macro throwing power is excellent, and it also levels off at low current densities. However, the coverage is inadequate. The cyanide bath is typically kept at room temperature, although it can be heated to 35 degrees Celsius to improve current efficiency. During the plating process, parts should be relocated. Silver anodes of high purity (>99.9%) should be used, and the anode to cathode ratio should be at least 1, with greater ratios preferred. To minimise undue silver accumulation in the bath, anodes should be withdrawn from the bath during prolonged nonoperational periods.
The plating procedure should begin with a silver strike, in which a less-silver-containing solution is utilised to prevent a silver-base metal exchange reaction. If the exchange reaction is allowed to proceed, a loosely adherent deposition will result. Silver striking takes a short period, usually under 1 minute, and the coating thickness is less than 0.25 m. Before using the plating tank, no rinsing is necessary.
Silver plating is generally treated after that to prevent tarnishing. If electrical conductivity is not necessary, bright lacquer or physical vapour deposition (PVD) coatings can be utilised. Chromate conversion coatings have been utilised in the past. However, the requirement to replace hexavalent chromium renders them unsuitable for cutlery.
Silver metal has the highest electric conductivity of all metals, although tarnishing and brighteners reduce it to around 55–60% of that of pure silver. Silver has solid lubricating qualities in low-lubricity fluids, as well as anti-galling and anti-seizing capabilities at high temperatures, which is why it’s used in jet engines. The coating’s reflective qualities are also good: it can reflect 90–95 per cent of visible and UV radiation.
Silver’s antibacterial qualities are widely known, and some of the most recent uses rely on its ability to improve communication equipment’ high-frequency properties. The usage of electroplated silver in electronics is expected to increase due to the lead prohibition and rising gold costs.