ASTM B368-21 PDF

Full title and description

ASTM B368-21 — Standard Test Method for Copper‑Accelerated Acetic Acid‑Salt Spray (Fog) Testing (CASS Test). This test method defines a copper‑accelerated acetic acid salt‑spray (CASS) fog environment and procedures for comparative evaluation of corrosion resistance of decorative electroplated coatings, anodized aluminium, zinc die‑castings and selected heavy‑duty plastics under an aggressive salt/mist environment.

Abstract

ASTM B368‑21 specifies the CASS (copper‑accelerated acetic acid salt spray) continuous‑fog corrosion test: preparation of the modified salt solution, addition of copper chloride, acidification with acetic acid, chamber and exposure conditions, specimen preparation notes, and recommended use cases (R&D, specification acceptance, production control and simulated service evaluation). The method is intended primarily for decorative electrodeposited systems (nickel/chrome and copper/nickel/chrome) and anodized aluminum, but may be applied to other materials where appropriate correlation with field performance has been established.

General information

• Status: Active.
• Publication date: 2021 (designation B368‑21; published January 4, 2021).
• Publisher: ASTM International (American Society for Testing and Materials).
• ICS / categories: 77.060 (Corrosion of metals) — corrosion testing / metallic coatings.
• Edition / version: B368‑21 (2021 edition).
• Number of pages: ~5 pages (short test method).

Scope

The standard defines the CASS test method — a continuous indirect fog of an acidified sodium chloride solution with added copper chloride — for evaluating relative corrosion resistance of decorative copper/nickel/chromium or nickel/chromium coatings on steel, zinc alloys, aluminum alloys and heavy‑duty plastics, and for anodized aluminum. The standard does not prescribe specific exposure durations or pass/fail acceptance criteria (these are agreed between purchaser and supplier or specified by a referencing specification).

Key topics and requirements

• Test name and purpose: Copper‑Accelerated Acetic Acid‑Salt Spray (CASS) continuous‑fog test for comparative corrosion evaluation.
• Test solution: prepare a 5% (w/v) NaCl solution (5 parts salt in 95 parts water), add copper(II) chloride dihydrate at the rate specified in the method (commonly 0.25 g/L or ~1 g per 4 L, per method guidance), then adjust pH to 3.1–3.3 with glacial acetic acid.
• Chamber conditions: exposure zone temperature typically ≈49 °C (49 ±1–2 °C); fog deposition rate target around 1.0–2.0 ml per 80 cm² per hour (check apparatus calibration).
• Specimen preparation: metallic and metallic‑coated specimens normally cleaned per method instructions; nonmetallic specimens handled per agreement to avoid solvent damage. Edges of multi‑layer or clad samples may be masked per guidance to avoid edge corrosion artifacts.
• Test duration and evaluation: duration is agreed between parties or specified by a product specification; visual inspection and defined acceptance criteria (e.g., blistering, discoloration, filiform, red rust) are applied per agreement or referencing standards.
• Applications: R&D, specification acceptance, production control and simulated service evaluation for coatings and alloy selection.
• Related practices and referenced standards: the method references other ASTM practices/specifications for cleaning, plating and coating descriptions (for example, practices/specs covering electrodeposited coatings).

Typical use and users

Users include corrosion and materials testing laboratories, electroplaters, coating formulators, anodizing shops, OEM quality and R&D teams (automotive, aerospace, consumer electronics, hardware/fasteners, architectural finishes), and purchasers specifying decorative chrome/nickel plating or anodized aluminium performance. The test is commonly invoked when rapid comparative data on coating/substrate corrosion resistance is required for acceptance or process control.

Related standards

Commonly referenced or complementary standards: ASTM B117 (neutral salt spray), ASTM G85 (cyclic and variant salt spray tests including acetic acid and SWAAT), ISO 9227 (salt spray / CASS variants), and coating specifications such as ASTM B456 (electrodeposited copper + nickel + chromium). Users frequently cite these standards alongside B368 when specifying corrosion testing programs.

Keywords

CASS; Copper‑accelerated; Acetic acid; Salt spray; Fog; Corrosion testing; Decorative plating; Anodized aluminium; Electroplating; ASTM B368‑21.

FAQ

Q: What is this standard?

A: ASTM B368‑21 is the ASTM standard test method that defines the copper‑accelerated acetic acid salt spray (CASS) continuous‑fog corrosion test used to compare corrosion resistance of decorative electroplated systems, anodized aluminum and related materials.

Q: What does it cover?

A: It covers preparation of the modified salt solution (5% NaCl with added copper chloride and acidified to pH 3.1–3.3), chamber conditions (about 49 °C), fog deposition targets, specimen preparation notes, and guidance on use cases — but does not set exposure durations or pass/fail criteria (those are set by contract or referencing specifications).

Q: Who typically uses it?

A: Corrosion laboratories, plating and finishing shops, coating formulators, OEM quality/R&D teams (automotive, aerospace, electronics, hardware, architectural finishes), and procurement/specification engineers.

Q: Is it current or superseded?

A: The designation B368‑21 indicates the 2021 revision; the method is listed as published/active in 2021 (B368‑21). Users should confirm they are calling out the 2021 edition in purchase orders or specifications.

Q: Is it part of a series?

A: It is part of the family of salt‑spray and corrosion test methods (ASTM B117, ASTM G85 variants, ISO 9227 and related practices), and is often referenced together with standards for electrodeposited coatings and inspection/cleaning practices.

Q: What are the key keywords?

A: CASS, copper‑accelerated, acetic acid, salt spray, fog, corrosion testing, decorative plating, anodized aluminium, ASTM B368‑21.