Chrome plating

Chrome plating is a surface treatment widely used in industry to improve the aesthetics, corrosion resistance and wear resistance of steel.

It consists of applying a layer of metallic chromium to the surface of a material (not only steel) through electrochemical or chemical processes. The chromium layer can have a variable thickness and its main functions are:

• Improve corrosion resistance.
• Increase surface hardness and wear resistance.
• Provide a shiny aesthetic finish.

There are two main types of chrome plating:

Decorative chrome plating: the chromium layer is thin (0.1-1 µm), applied over a nickel layer to improve aesthetics and protection.

Hard chrome plating: the chromium layer is thick (up to 500 µm) and is used to improve hardness and wear resistance, often on industrial components.

Differences between Stainless and Chrome Steel

Stainless Steel

Stainless steel is an alloy of iron, carbon and at least 10.5% chromium, with possible additions of nickel, molybdenum or titanium. The chromium present in the alloy forms a passive layer on the surface that protects the material from corrosion without the need for further treatments.

Main properties:

• Intrinsic resistance to corrosion.
• Easy to clean and hygienic.
• Does not require specific maintenance to preserve its characteristics.

Disadvantages:

• Higher cost than common steel.
• Not suitable for extreme surface hardness requirements.

Chrome Steel

Chrome steel is a common steel (not stainless steel) that is coated with a layer of chromium by chromium plating.

Main properties:

• Better resistance to corrosion than untreated steel.
• High surface hardness and wear resistance (especially with hard chrome plating).
• Cheaper than stainless steel.

Disadvantages:

• If the chromium layer is damaged, corrosion can spread rapidly.
• Greater vulnerability to breakage than stainless steel, which is homogeneous.

Chrome Plating Process

Chromium plating is mainly done by electroplating in galvanic baths. Here are the main phases:

Surface preparation:

• The surface is cleaned and degreased to remove any impurities.
• Sandblasting or sanding is performed to ensure optimal adhesion.

Galvanic bath:

• The piece is immersed in a solution containing chromic acid (CrO₃) and catalysts.
• The electric current deposits the metallic chromium on the surface of the piece.

Rinsing and finishing:

• After chrome plating, the piece is rinsed to remove chemical residues.
• Any polishing or final treatments improve the appearance and quality.

Chrome Plating Plants

Industrial chrome plating plants consist of:

1. Galvanic tanks: They contain the electrolytic solution and are equipped with handling systems to facilitate the treatment of large pieces.
2. Purification plants: They manage chemical residues and comply with environmental regulations. Chrome plating uses hexavalent chromium, a toxic substance that requires rigorous control systems to avoid contamination.
3. Control units: Monitor temperature, solution concentration, and current intensity to ensure uniform treatment.
4. Automation systems: Automate the process to increase productivity and reduce errors.

Uses of Chrome Steel

Mechanical industry

• Machinery components: shafts, pistons, rollers and valves. Hard chrome plating improves wear resistance.
• Cutting tools: increases hardness and reduces friction.

Automotive

• Aesthetic parts: bumpers, grilles, rims.
• Functional components: pistons and gears to improve performance.

Medical sector

• Surgical instruments and equipment that require durable and easily sterilizable surfaces.

Furniture and design

• Decorative elements such as furniture, lamps, handles and taps.

Insights

Chromium plating can also be applied to metals other than steel, depending on technical and aesthetic needs. Below are the main metals that can be chromed and the reasons for doing so:

Aluminum: Aluminum is chromed to increase corrosion resistance and improve aesthetics, especially in the automotive and furniture sectors. Since aluminum is softer than steel, hard chrome plating is often used to increase its surface hardness. Examples of applications: car rims, bicycle components, decorative and design elements.

Copper: Copper is chromed primarily to protect it from oxidation, which would otherwise lead to the characteristic green patina. Chrome plating is also used to improve hardness and reduce wear. Examples of applications: electrical contacts, aesthetic and decorative components.

Brass: Brass, an alloy of copper and zinc, is often chromed for aesthetic purposes (for example, to obtain a shiny and resistant finish) and to prevent oxidation. Chrome plating is common in the plumbing and furniture accessory industries. Examples of applications: faucets and mixers, door and window handles, decorative elements.

Zinc: Zinc is sometimes chromated to improve corrosion resistance, especially when used in aggressive environments. However, chromium plating on zinc is less common than galvanizing or other protective coatings. Examples of applications: aerospace or automotive components.

Nickel and Nickel-Phosphorus: In some cases, nickel or nickel-phosphorus is chromated to achieve specific properties such as increased chemical resistance or improved aesthetic performance. This approach is often used in industrial components. Examples of applications: precision instruments, mechanical components subject to high wear.

Magnesium: Magnesium is a lightweight but highly reactive metal. Chrome plating is used to protect it from corrosion and improve its appearance. It is common in the aerospace and automotive industries. Examples of applications: racing car parts, lightweight aircraft components.

Iron and Cast Iron: Iron and cast iron are chromated mainly to increase wear and corrosion resistance, as well as to improve the life of mechanical components. Application examples: rolling mill rollers, hydraulic pistons, industrial machine cylinders.