Coating designation according to ISO 4527

Correctly designating the electroless nickel plating treatment is essential to ensure that the applied coating is consistent with the component’s functional requirements.
An incomplete or ambiguous specification can lead to different interpretations between the designer, the workshop, and the plating provider, with the risk of insufficient performance, dimensional issues, or non-conformities.

For traditional electroless nickel coatings, the main reference standard is ISO 4527, which defines a standardized method for designating autocatalytic nickel–phosphorus alloy coatings.

ISO 4527 standard

ISO 4527 – Autocatalytic (electroless) nickel-phosphorus alloy coatings establishes how to uniquely indicate the main characteristics of the treatment, enabling clear communication throughout the supply chain.

Using the designation according to ISO 4527 makes it possible to specify:

• the base material;
• the type of Ni–P coating (phosphorus content);
• the minimum thickness of the deposit;
• any post-deposition heat treatment.

The standard applies to traditional electroless nickel coatings in the NIPLATE® 500, NIPLATE® eXtreme and NIPLATE® 600 families.

ISO 4527 does not cover composite coatings, such as NIPLATE® 500 PTFE and NIPLATE® 600 SiC, which require a dedicated technical specification.

Designation structure according to ISO 4527

The treatment designation, to be shown in the title block of the technical drawing or in the supply specification, is structured as follows:

Autocatalytic nickel coating ISO 4527 – a<b>/NiP(c)d[e(f)g]

Each part of the designation has a specific meaning.

Base material – a<b>/

The first part indicates the base material to be coated:

• a is the chemical symbol of the main element (e.g., Fe for steels);
• b is the alloy designation (e.g., S235JR, 18NiCrMo5).

Example:

Fe<18NiCrMo5>/

Ni–P coating – NiP(c)d

This part defines the characteristics of the electroless nickel coating:

• c indicates the nominal phosphorus content as a percentage;
• d indicates the minimum coating thickness, expressed in micrometres (µm).

References to NIPLATE® coatings:

• NIPLATE® 500 and NIPLATE® eXtreme → NiP(11)
• NIPLATE® 600 → NiP(7)

For composite coatings, since they are not covered by the standard, descriptive indications such as the following can be used:

• NiP(PTFE)
• NiP(SiC)

Heat treatment – [e(f)g]

The last part of the designation refers to any post-plating heat treatment:

• e indicates the type of treatment:
  • ER = dehydrogenation
  • HT = hardening treatment
• f indicates the temperature in °C
• g indicates the duration in hours

Common examples:

• Dehydrogenation: [ER(150)4]
• Hardening: [HT(260)8]
• Hardening: [HT(330)4]

Complete designation example

A NIPLATE® 600 electroless nickel plating treatment, with a thickness of 20–25 µm, subjected to hardening treatment at 340 °C for 4 hours, on 18NiCrMo5 steel, can be designated as:

Autocatalytic nickel coating ISO 4527 – Fe<18NiCrMo5>/NiP(7)20[HT(340)4]
Thickness: 20–25 µm – Hardness: 1000 ± 50 HV

This example highlights how the ISO designation is the basis of the specification, but does not fully cover all technical requirements.