ASTM A380 is the standard practice that governs cleaning, descaling and passivation of stainless steel parts, equipment and systems. Where ASTM A967 specifies the passivation treatment itself, A380 covers everything around it: how to remove grease, scale, weld heat tint and embedded iron before treatment, which cleaning methods are acceptable, and how to verify the result. If a specification calls only for “passivation to A967” on a system that has just been welded, it is incomplete — A380 is the standard that tells you how to get the surface clean enough for A967 to work.
What is ASTM A380?
ASTM A380 / A380M is titled Standard Practice for Cleaning, Descaling, and Passivation of Stainless Steel Parts, Equipment, and Systems. It is a practice rather than a specification, which matters: it describes accepted methods and gives guidance on selecting between them, rather than dictating a single acceptance number.
Its scope covers the whole surface-preparation sequence. That includes degreasing and removal of organic soils, removal of mill scale and weld scale, removal of weld heat tint, removal of embedded iron and other foreign particles, the chemical treatments used for each, the water quality used for rinsing, and the inspection methods used to confirm the surface is clean. It applies to parts on a bench and to installed piping systems alike, which is why it is the reference standard for field work on process and high-purity water systems.
The most common practical use of A380 in our work is as the governing document for pre-passivation cleaning on newly fabricated stainless piping, and as the reference for the inspection tests that demonstrate the cleaning worked.
ASTM A380 vs ASTM A967 — which standard applies?
This is the question we are asked most often, and getting it wrong is the reason a lot of passivation scopes under-deliver. The two standards are complementary, not alternatives.
| ASTM A380 | ASTM A967 | |
|---|---|---|
| Document type | Standard Practice | Standard Specification |
| Primary subject | Cleaning, descaling and passivation | Chemical passivation treatments |
| Covers degreasing | Yes | No |
| Covers scale and heat tint removal | Yes | No — requires it to be done first |
| Defines specific treatment methods | General guidance | Yes — ten methods, C1–C5 and N1–N5 |
| Defines acceptance tests | Yes — inspection practices | Yes — test methods and criteria |
| Base metal removal | Pickling does remove metal | None |
| Typical use | How to prepare and verify the surface | What treatment to specify and how to prove it |
The correct construction for a specification is usually both: clean and descale in accordance with ASTM A380, then passivate in accordance with ASTM A967 Method C1 (or whichever method the service requires), and verify to the acceptance criteria of both.
What is descaling, and when is it required?
Descaling is the removal of the heavy, adherent oxide scale produced by hot working, annealing, or welding. It is a more aggressive operation than either cleaning or passivation, and it is required whenever visible scale or heat tint is present.
The distinction that matters on a jobsite is between scale and tint. Mill scale is thick, dark and obvious. Weld heat tint is thin — typically 20 to 100 nanometres — and shows as straw, gold, blue or violet coloring adjacent to a weld. Both are chromium-depleted, both are removed under A380, and neither will be removed by passivation chemistry. A surface passivated over heat tint is a surface with corrosion initiation sites designed into it.
What cleaning methods does ASTM A380 cover?
A380 groups methods by what they are intended to remove. Selecting the wrong family is the usual cause of a failed inspection.
| Method family | Removes | Typical chemistry or means | Removes base metal? |
|---|---|---|---|
| Degreasing / alkaline cleaning | Oils, greases, cutting fluids, organic soils | Alkaline detergent, 2–4%, 140–160 °F, 30–45 min | No |
| Mechanical cleaning | Heavy scale, weld spatter, gross contamination | Abrasive blasting, grinding, brushing with stainless media only | Yes — uncontrolled |
| Acid pickling | Mill scale, weld scale, heavy heat tint | 10–25% HNO3 with 1–3% HF, ambient to 140 °F, 30–120 min | Yes — 5 to 50+ µm |
| Passivation | Free iron; restores chromium oxide film | 4–10% citric or 20–25% HNO3, 140–160 °F, 30–60 min | No |
| Electropolishing | Surface iron; smooths and enriches chromium | Electrolytic, per ASTM B912 | Yes — controlled, a few µm |
| Final rinse | Residual chemistry | Deionized or WFI-quality water to specified conductivity | No |
One rule cuts across all of them: never use carbon steel tooling, brushes or abrasive media on stainless. Iron transferred from a carbon-steel wire brush embeds in the surface and produces rust spotting within days. A380 is explicit that only stainless or non-metallic media may contact the surface.
What is the difference between pickling and passivation?
They are routinely written into specifications as though interchangeable. They are not.
| Pickling | Passivation | |
|---|---|---|
| Purpose | Remove scale and heat tint | Remove free iron, restore passive layer |
| Chemistry | 10–25% nitric with 1–3% hydrofluoric | 4–10% citric, or 20–25% nitric |
| Temperature | Ambient to 140 °F | 140–160 °F (citric) |
| Contact time | 30–120 minutes | 30–60 minutes |
| Base metal removed | 5 to 50+ micrometers | None |
| Effect on surface finish | Dulls and roughens the surface | No measurable change |
| Hazard profile | High — hydrofluoric acid | Low with citric; moderate with nitric |
| Governing standard | ASTM A380 | ASTM A967 |
Because pickling removes measurable base metal and roughens the surface, it is generally avoided on finished product-contact surfaces where a specified Ra must be maintained. On an ASME BPE system with an SF4 finish requirement, pickling a section of tube can put you out of specification on surface roughness even though the scale is gone.
Do I need to pickle before passivating?
Only if scale or heat tint is present. On a clean, machined or as-supplied mill-finish surface carrying nothing worse than handling soils and free iron, degreasing followed by passivation is sufficient and is the normal sequence.
Pickling becomes necessary when the surface carries weld scale, heavy heat tint, or oxide from heat treatment. The decision is straightforward: if you can see color or scale after degreasing, passivation alone will not remove it.
Where heat tint is light, mechanical removal with stainless media or an electrochemical weld-cleaning unit is often preferable to full pickling, because it is localized, avoids hydrofluoric acid handling, and does not affect the finish of the surrounding tube.
What inspection and acceptance tests does ASTM A380 define?
A380 sets out the practices used to demonstrate that cleaning worked. These are the tests that belong in a turnover package.
| Test | What it detects | Method and duration | Pass criterion |
|---|---|---|---|
| Water break test | Residual oil or organic film | Flood the surface with clean water | Continuous unbroken film held ≥30 seconds |
| Copper sulfate test | Free iron on the surface | 6% solution applied for 6 minutes | No copper-colored deposit |
| Ferroxyl test | Free iron, higher sensitivity | Potassium ferricyanide solution | No blue coloration within 30–60 seconds |
| High humidity test | Residual contamination | 100% relative humidity, 100 °F, 24 hours | No rust or staining |
| Water immersion test | Residual contamination | 100–170 °F, 24 hours | No rust or staining |
| Salt spray (ASTM B117) | Corrosion resistance | 5% NaCl at 95 °F, 24–72 hours | No corrosion within the specified period |
| Visual inspection | Scale, tint, spotting, weld defects | Direct or borescope, under adequate light | No visible scale, tint or foreign matter |
| Rinse water analysis | Residual chemistry | Conductivity and pH of final rinse | Typically pH 6.5–7.5 and <2 µS/cm |
Does ASTM A380 apply to weld heat tint?
Yes, and this is one of its most important provisions. A380 requires that heat tint and oxide scale be removed before passivation. Passivation chemistry — whether citric or nitric — will not remove heat tint, and applying it over tint produces a surface that looks treated and is not.
The color of the tint indicates roughly how hot the metal got and how thick the oxide is: pale straw around 400–500 °F at about 20 nanometres, gold to tan at 500–600 °F, blue and violet at 600–900 °F approaching 100 nanometres, and dark scale above 1,100 °F. Anything beyond the palest straw should be removed on a product-contact surface.
Prevention is cheaper than removal. Adequate inert gas purge on the weld interior — and holding purge until the weld zone cools below the tinting temperature — keeps tint from forming at all.
What documentation should an A380 scope produce?
A cleaning operation that cannot be evidenced is difficult to defend in an audit. A complete turnover package for A380 work should contain, at minimum:
- The written procedure actually executed, including chemistry, concentration, temperature, contact time and flow rate
- Batch or lot certification for every chemical used
- Calibration records for the instruments used to verify temperature, conductivity and pH
- Recorded process parameters for each circuit or section treated, not a single blanket entry
- Final rinse water quality results, with the acceptance limit stated
- Inspection results for each acceptance test performed, identified by location
- A drawing or line list identifying exactly which circuits were treated
- Deviation records and their disposition, where parameters fell outside the procedure
For pharmaceutical and biotech systems this package usually forms part of the installation qualification file, which is why the line list and the calibration records matter as much as the chemistry.
How does A380 relate to ASME BPE and the CFR?
ASME BPE governs the design and construction of bioprocessing equipment, including surface finish designations and the minimum surface chromium-to-iron ratio of 1.3 to 1. A380 and A967 are the practices by which that surface condition is achieved and verified. BPE tells you what the surface must be; A380 and A967 tell you how to get it there.
On the regulatory side, 21 CFR 211.67 requires equipment to be cleaned and maintained at appropriate intervals to prevent contamination that would alter product quality, and 21 CFR 211.63 requires equipment to be of appropriate design and suitably located to facilitate cleaning. A documented A380 cleaning with recorded acceptance testing is the practical evidence that those requirements have been met at installation.
For food contact surfaces, 3-A Sanitary Standards and EHEDG guidance impose comparable surface and cleanability expectations, and A380 remains the accepted practice for achieving them on stainless.
Need ASTM A380 cleaning and passivation on a real system?
Paul Industries cleans, descales, passivates and documents stainless steel process and high-purity water systems nationwide — new construction and systems already in GMP service. We work to written procedures, record the parameters as executed, and hand over the acceptance test results with the line list they belong to.
Frequently asked questions about ASTM A380
What is ASTM A380?
ASTM A380 is the Standard Practice for Cleaning, Descaling, and Passivation of Stainless Steel Parts, Equipment, and Systems. It covers degreasing, removal of mill scale, weld scale and heat tint, removal of embedded iron, the chemical and mechanical methods used for each, rinse water quality, and the inspection tests used to verify the result.
What is the difference between ASTM A380 and ASTM A967?
A380 is a practice covering how to clean, descale and prepare a stainless surface and how to verify it. A967 is a specification defining the passivation treatments themselves, including the ten methods C1 to C5 and N1 to N5, and their acceptance criteria. Most complete specifications cite both: clean and descale to A380, then passivate to A967.
Does ASTM A380 remove weld heat tint?
Yes. A380 covers removal of heat tint and requires it to be removed before passivation. Passivation chemistry will not remove heat tint, so a surface passivated over tint retains a chromium-depleted layer and the corrosion initiation sites that come with it.
What is the difference between pickling and passivation?
Pickling uses 10 to 25 percent nitric acid with 1 to 3 percent hydrofluoric acid to remove scale and heat tint, and removes 5 to 50 or more micrometers of base metal while dulling the surface. Passivation uses 4 to 10 percent citric or 20 to 25 percent nitric acid to remove free iron and restore the chromium oxide layer, and removes no measurable base metal.
Do I have to pickle before passivating?
Only when scale or heat tint is present. If degreasing leaves a clean surface with no visible color or scale, passivation alone is sufficient. If color or scale remains after degreasing, passivation will not remove it and pickling or mechanical removal is required first.
What is a water break test and what is the pass criterion?
A water break test floods the surface with clean water to detect residual oil or organic film. The surface passes if the water forms a continuous, unbroken film that holds for at least 30 seconds. Beading or breaking of the film indicates remaining organic contamination.
What is the copper sulfate test?
The copper sulfate test detects free iron on a stainless surface. A 6 percent copper sulfate solution is applied and left for 6 minutes. Any copper-colored deposit indicates free iron remains and the surface has not been adequately cleaned or passivated.
Can I use a carbon steel wire brush on stainless steel?
No. Carbon steel tooling, brushes and abrasive media transfer iron into the stainless surface, which then rusts. ASTM A380 requires that only stainless steel or non-metallic media contact the surface. This is one of the most common causes of rust spotting on newly fabricated systems.
What rinse water quality does A380 require?
A380 requires a final rinse with water of a quality that will not recontaminate the surface, and the acceptance limit is set in the project specification. In pharmaceutical work the final rinse is typically deionized or WFI-quality water, with acceptance around pH 6.5 to 7.5 and conductivity below 2 microsiemens per centimeter.
Is ASTM A380 required by the FDA?
A380 is not named in the regulations. However 21 CFR 211.63 requires equipment of appropriate design to facilitate cleaning, and 21 CFR 211.67 requires cleaning and maintenance that prevents contamination altering product quality. A documented A380 cleaning with recorded acceptance testing is the practical evidence used to demonstrate compliance at installation.
Does A380 apply to installed piping systems or only to parts?
Both, and that breadth is what distinguishes it from ASTM A967. A380 is a standard practice covering cleaning, descaling and passivation of stainless steel parts, equipment and systems, so it addresses installed pipework and vessels as well as discrete components. It also covers the steps A967 does not, principally removal of heat tint and weld scale, which passivation chemistry alone will not clear. Thorough specifications cite both: A380 for surface preparation, A967 for the passivation treatment and its verification.
What documentation should an ASTM A380 cleaning produce?
The turnover package should include the executed procedure with chemistry, concentration, temperature, contact time and flow rate; chemical batch certifications; instrument calibration records; recorded parameters per circuit; final rinse water results; acceptance test results identified by location; a line list of circuits treated; and any deviation records with their disposition.