ASTM B456
Standard Specification for Electrodeposited Coatings of Copper Plus Nickel Plus Chromium and Nickel Plus Chromium
Specifies decorative and protective copper-nickel-chromium or nickel-chromium systems on specified metal substrates.
What ASTM B456 specifies
ASTM B456 is the principal decorative chromium system specification for metal substrates. SC1 through SC5 represent mild through extended very severe service, but the required copper and nickel construction depends on substrate. On steel without copper, representative minimum nickel thicknesses are 10, 15–20, 25, 30, and 35 µm as service rises from SC1 to SC5. Chromium may be regular, microcracked, or microporous; the discontinuous forms improve corrosion distribution. Buyers should state substrate, service condition, full classification number, appearance, significant surfaces, and rack-mark locations. The standard does not cover plating on plastics.
ASTM B456 types and classes
Every designation the document defines, with the thickness it requires and the tests it imposes.
| Designation | Meaning | Thickness | Requirement / test |
|---|---|---|---|
SC1 | Mild indoor service; steel Ni-Cr system uses 10 µm minimum nickel. | ≥ 10 µm ≥ 0.39 mil | Thickness, adhesion, and appearance. |
SC2 | Moderate service; steel uses 20 µm bright nickel or 15 µm duplex nickel. | ≥ 15 µm ≥ 0.59 mil | Thickness, adhesion, and applicable corrosion test. |
SC3 | Severe service; steel Ni-Cr system uses 25 µm minimum duplex nickel. | ≥ 25 µm ≥ 0.98 mil | CASS or specified corrosion test plus thickness. |
SC4 | Very severe service; steel Ni-Cr system uses 30 µm minimum duplex nickel. | ≥ 30 µm ≥ 1.2 mil | CASS or specified corrosion test plus thickness. |
SC5 | Highest service category; steel Ni-Cr system uses 35 µm minimum duplex nickel. | ≥ 35 µm ≥ 1.4 mil | CASS or specified corrosion test plus thickness. |
Tests and the drawing call-out
Tests the document imposes
- Layer thickness
- Adhesion by ASTM B571
- Copper elongation and nickel ductility
- CASS or Corrodkote corrosion testing
- Nickel sulfur content and STEP potential
- Chromium crack or pore density
How to cite it
Drawing call-out
DECORATIVE <Cu-Ni-Cr|Ni-Cr> PER ASTM B456, SC<1|2|3|4|5>, CLASSIFICATION <SYSTEM CODE>, <APPEARANCE>Angle brackets mark the choices the drawing must make; every finish page shows a completed example.
Finishes specified to ASTM B456
ASTM B456 — frequently asked
What does SC3 mean?
SC3 means severe service. The exact layer stack and thickness still depend on the substrate and selected classification number.
Does the chromium supply most corrosion protection?
No. The nickel system supplies most thickness and barrier protection; the thin chromium topcoat supplies appearance and tarnish and scratch resistance.
Can ASTM B456 be used for plated ABS?
No. The standard explicitly does not cover plating on plastics, even though similar copper-nickel-chromium stacks are commercially used on ABS.
ASTM B456 is copyrighted by ASTM International. This page explains the document so a drawing can be read; it does not reproduce the standard. Purchase the current edition from the publisher. Official source ↗