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ASTM A967 Passivation Standard: Complete 2025 Guide | CXP Solutions NC
Industry Standard Reference • Updated 2025

ASTM A967
Passivation Standard:
Complete Technical Guide

The definitive technical reference covering all 10 citric and nitric acid methods, testing procedures, acceptance criteria, and industry applications. Expert passivation services across North Carolina and the Southeast.

Explore All 10 Methods Request Quote
📊 Passivation Performance
1.8:1
Cr:Fe Ratio

CXP citric acid passivation achieves Cr:Fe ratios of 1.7–2.0+, exceeding the ASME BPE minimum of 1.3:1 for pharmaceutical systems.

1.0:1 ASME BPE Min: 1.3:1 2.0:1+
📅ASTM A967 first published 2001, replacing QQ-P-35C
🧪10 methods: 5 citric acid, 5 nitric acid
🌿Citric acid is FDA GRAS rated
📊Passive layer only 1–5 nanometers thick
⚡CXP uses citric acid for 90%+ of projects
📋ASME BPE requires Cr:Fe ≥1.3:1
📅ASTM A967 first published 2001, replacing QQ-P-35C
🧪10 methods: 5 citric acid, 5 nitric acid
🌿Citric acid is FDA GRAS rated
📊Passive layer only 1–5 nanometers thick
✓
ASTM A967 Compliant
✓
Zero Accidents 10+ Years
✓
NC Based, Nationwide Service
✓
Full cGMP Documentation
✓
Owner-Led Execution
Technical Foundation

Understanding ASTM A967

ASTM A967/A967M is the authoritative standard specification for chemical passivation treatments applied to stainless steel parts. Published by ASTM International, it defines the chemistry, process parameters, and acceptance criteria that ensure consistent, high-quality passive layers on stainless steel surfaces.

The standard replaced the obsolete military specification QQ-P-35C in 2005, modernizing passivation requirements and — critically — adding citric acid methods alongside traditional nitric acid processes. This was a major advancement, as citric acid offers superior performance with significantly reduced environmental and safety concerns.

For a comprehensive guide covering the complete passivation process including failure modes and documentation requirements, see our Complete Passivation Master Guide.

💡 Key Insight: Cr:Fe Ratio

A properly passivated surface achieves a chromium-to-iron ratio (Cr:Fe) of 1.5:1 or higher. CXP routinely achieves 1.7–2.0+ using citric acid methods, exceeding ASME BPE requirements for pharmaceutical systems.

📍 CXP Service Coverage

Based in Sanford, North Carolina, we provide ASTM A967 compliant passivation throughout the Southeast and nationwide.

🔶 North Carolina 🔶 South Carolina 🔶 Virginia 🔶 Georgia 🔶 Tennessee 🔶 Nationwide
Stainless steel piping with TIG welded flange requiring ASTM A967 passivation
2001
First publication of ASTM A967, replacing the obsolete QQ-P-35C military specification
Core Specification

All 10 ASTM A967 Methods

ASTM A967 defines five citric acid methods and five nitric acid methods. Select a chemistry type below, then click any method to see detailed parameters.

⚗️
Method Explorer
🌿

Why Citric Acid is Preferred

Citric acid produces superior Cr:Fe ratios (1.7–2.0+ vs 1.4–1.6 for nitric), is FDA GRAS-rated, has no hazardous fumes, and costs 60–80% less for disposal. CXP uses citric for 90%+ of pharmaceutical and food-grade applications. Compare Citric vs Nitric →

C1
Citric 1
High-Volume
C2
Citric 2
CXP Standard
C3
Citric 3
Ambient
C4
Citric 4
Custom
C5
Citric 5
pH Control
C1
Citric 1 - High Temperature, Short Duration
4–10%
Concentration
140–160°F
Temperature
4 min
Min. Time
≤2.2
pH Range
Best For: High-volume production environments where throughput is critical. The elevated temperature accelerates iron dissolution, allowing shorter contact times. Use our Time/Temperature Calculator to optimize parameters.
⚠️

Safety Considerations for Nitric Acid

Nitric acid generates hazardous NOx fumes requiring ventilation and scrubber systems. Full PPE including respirators and acid-resistant suits are mandatory. Disposal costs are significantly higher due to EPA hazardous waste regulations.

N1
Nitric 1
+ Dichromate
N2
Nitric 2
Most Common
N3
Nitric 3
Elevated Temp
N4
Nitric 4
High Conc.
N5
Nitric 5
Custom
N1
Nitric 1 - With Sodium Dichromate
20–25%
HNO₃ Conc.
120–130°F
Temperature
20 min
Min. Time
2–3%
Dichromate
⚠️ Warning: Contains sodium dichromate (Cr⁶⁺), a known carcinogen. Most industries have moved away from this method. CXP can provide equivalent or superior results using safer citric acid alternatives.
Cr:Fe ≥1.3
ASME BPE minimum Cr:Fe ratio requirement — CXP typically achieves 1.7–2.0+
Verification Requirements

Testing & Acceptance Criteria

ASTM A967 specifies multiple acceptance tests. Click each card to learn the procedure and pass criteria.

💧

Water Immersion

24-hour submersion test at elevated temperature

↻ Click to flip

Water Immersion Test

Procedure: Immerse parts in Type I deionized water at 100–170°F for 24 hours. Remove and examine surface for rust stains, discoloration, or corrosion products.

✓ Pass Criteria
No visible rust staining or corrosion
🌫️

High Humidity

Accelerated 100% RH exposure test

↻ Click to flip

High Humidity Test

Procedure: Expose parts to 100% relative humidity at 100°F for 24 hours in a controlled environmental chamber. Examine surface after exposure.

✓ Pass Criteria
No rust visible to the naked eye
🧂

Salt Spray

ASTM B117 accelerated corrosion test

↻ Click to flip

Salt Spray Test (ASTM B117)

Procedure: Expose to 5% sodium chloride salt spray at 95°F for 24–72 hours per ASTM B117. Examine for corrosion after rinsing.

✓ Pass Criteria
No rust. White salt deposits are acceptable.
🔶

Copper Sulfate

Quick field verification test

↻ Click to flip

Copper Sulfate Test

Procedure: Apply acidified copper sulfate solution (CuSO₄ + H₂SO₄) to surface for 6 minutes. Wipe clean and examine for copper-colored deposits.

✓ Pass Criteria
No copper-colored (pink) deposits
🔵

Ferroxyl Test

Detects free iron contamination

↻ Click to flip

Ferroxyl (Potassium Ferricyanide)

Procedure: Apply potassium ferricyanide solution to surface. Blue spots indicate presence of free iron contamination that passivation failed to remove.

✓ Pass Criteria
No blue spots or discoloration
🔬

XPS/AES Analysis

Lab analysis for Cr:Fe ratio

↻ Click to flip

XPS/AES Surface Analysis

Procedure: Laboratory spectroscopy analysis measuring actual chromium-to-iron ratio on the surface. Most precise quantitative method available.

✓ Pass Criteria
Cr:Fe ratio ≥1.3:1 (ASME BPE)
📋 CXP Testing Protocol

Every CXP project includes verification beyond A967 minimums: visual inspection, ferroxyl testing on welds, pH/conductivity verification, and documented photography. Use our Time/Temperature Calculator to optimize parameters.

Complete Workflow

6-Step Passivation Process

CXP follows a structured, repeatable workflow for every ASTM A967 passivation project.

1

Pre-Clean & Degrease

Alkaline degreasing at 140–160°F removes fabrication oils and cutting fluids.

🌡️ 140–160°F ⏱️ 30–45 min
2

Pre-Passivation Rinse

DI/RO water rinse cycles until pH stabilizes at 6.5–7.5.

💧 DI Water ⚖️ pH 6.5–7.5
3

Passivation Treatment

4–10% citric acid circulation at 140–160°F for 30–60 minutes.

🧪 4–10% ⏱️ 30–60 min
4

Post-Passivation Rinse

Multiple rinse cycles until pH returns to neutral and conductivity matches source.

💧 <2 µS/cm ⚖️ pH 6.5–7.5
5

Drying & Protection

System drained and blown dry with filtered air or N₂ purge.

💨 Filtered Air 🛡️ N₂ Option
6

Verification & Docs

Testing per ASTM A380, complete documentation package.

📋 Audit-Ready 📸 Photos
Standards Comparison

ASTM A967 vs A380 vs QQ-P-35C

Understanding how these related standards work together for complete passivation programs.

Attribute ASTM A967 ASTM A380 QQ-P-35C
Purpose Passivation specification Cleaning & surface prep Obsolete military spec
Status Current Standard Current Standard Cancelled 2005
Chemistry 10 methods defined References A967 Nitric only
Testing Detailed test methods Acceptance criteria Basic requirements
Citric Acid 5 Methods Supported Not Included
CXP Reference Primary passivation spec Testing & cleaning Legacy reference only

📋 When to Reference Each Standard

Use ASTM A967 For:

Specifying passivation requirements in purchase orders, contracts, or quality specs. Primary reference for chemistry, parameters, and acceptance testing.

Use ASTM A380 For:

Complete cleaning and surface preparation practices. References A967 for passivation. Use when specifying full pre-treatment sequence including degreasing.

Common Questions

ASTM A967 FAQ

Not legally required for all applications, but strongly recommended for any system requiring corrosion resistance, cleanliness, or regulatory compliance. Mandatory for pharmaceutical (FDA cGMP), medical device (FDA 21 CFR 820), food processing (3-A SSI), and aerospace applications.
For most applications, citric acid is preferred. It produces superior Cr:Fe ratios (1.7–2.0+), is FDA GRAS-rated, has no hazardous fumes, and costs 60–80% less for disposal. CXP recommends Citric 2 as the default for pharmaceutical, food, and general industrial. See our detailed comparison guide.
A properly passivated surface should not require re-passivation under normal operating conditions. However, re-passivation is needed after: welding or mechanical modification, chemical damage or contamination, rouge formation, or when specified by preventive maintenance programs.
QQ-P-35C was officially cancelled in 2005 and replaced by ASTM A967. While some legacy specifications still reference it, all new work should cite ASTM A967 which provides superior coverage including citric acid methods not available in the obsolete military spec.
Yes. While based in Sanford, NC, CXP provides mobile passivation services throughout the Southeast (SC, VA, GA, TN) and nationwide for larger projects. Our mobile CIP equipment allows complete on-site passivation without removing equipment. Contact us with your project location for a custom quote.
Every CXP project includes a complete documentation package: executed protocols with signatures, time/temperature logs, pH/conductivity curves, verification test results with photographs, chemical lot certifications, and final QA sign-off. Documentation meets FDA 21 CFR Part 11 requirements.

Need ASTM A967 Passivation?

CXP Solutions delivers citric and nitric acid passivation services with comprehensive documentation, Cr:Fe ratio verification, and acceptance testing. Mobile deployment from North Carolina to nationwide.

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Facilities Served
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Related Resources

📘

Complete Passivation Master Guide

The definitive 10-chapter technical resource on stainless steel passivation.
⚖️

Citric vs Nitric Comparison

Detailed side-by-side analysis of both passivation chemistries.
🧮

Chemical Dilution Calculator

Calculate precise solution concentrations for passivation chemistry.
🔴

Derouging Services

Rouge removal and re-passivation for contaminated systems.
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