Anodizing, conversion & passivation · finish comparison
Citric Acid Passivation vs Electropolishing
Citric Acid Passivation and Electropolishing are both passivation & electropolishing finishes; electropolishing resists corrosion better.
Citric Acid Passivation
Passivation & electropolishing · $
Citric-acid passivation is a separately searched and specified stainless-steel passivation route that removes free iron without nitric acid.
Electropolishing
Passivation & electropolishing · $$$ · instant quote
Electropolishing is controlled anodic dissolution that brightens, deburrs, and smooths stainless steel and other qualified alloys.
When to choose which
Choose Citric passivation
Citric passivation is the pick when its strengths below matter more than Electropolishing's.
- Adds 0 µm measurable buildup
- Avoids nitric-acid fumes and nitrate waste
- ASTM A967 provides multiple citric treatment windows
Choose Electropolishing
Choose Electropolishing when smoothing is required.
- Removes about 5–25 µm per surface
- Reduces microscopic peaks and cleanability traps
- Deburrs very small edges without embedded abrasive
What the numbers say
- Electropolishing resists corrosion better.
- Citric passivation is the lower-cost option ($).
- Electropolishing is the thinner coating (removes 5–25 µm), so it disturbs tight fits less.
Scores side by side
Each score is 0–100 against every finish in this catalog. Corrosion is derived from salt-spray test duration and surface hardness from the finish layer's Vickers hardness where a measured figure exists; a finish that leaves the base metal's own surface is not rated for hardness. Cosmetic, lubricity and cost are FabDigit's engineering assessment. Scores and typical figures are screening data, not matched side-by-side tests or service-life rankings; ASTM B117 is a controlled salt-fog method, not a field-life prediction.
| Score | Citric passivation | Electropolishing |
|---|---|---|
| Corrosion resistance | 34 Low | 45 Fair |
| Surface hardness / wear | — — | — — |
| Cosmetic quality | 18 Low | 82 Very good |
| Lubricity | 10 Minimal | 35 Fair |
| Cost | 12 $ | 54 $$$ |
Key numbers
| Property | Citric passivation | Electropolishing |
|---|---|---|
| Thickness | 0 µm | removes 5–25 µm |
| Electrical | Unchanged | Unchanged |
| Relative cost | Budget ($) | Premium ($$$) |
| Added lead time | 2–4 working days | 3–6 working days |
| RoHS | Compliant | Compliant |
| Instant quote | On request | Yes |
Bold marks the side that is ahead on a row where more (or less, for cost and lead time) is better. Ranges are the typical specification window; the drawing call-out fixes the class.
Which materials take each finish
| Material family | Citric passivation | Electropolishing |
|---|---|---|
| Stainless Steel | Yes | Yes |
| Cobalt-Chrome Alloy | — | With care |
| DMLS / SLM | With care | With care |
| Nickel Alloy | — | With care |
| Aluminum | No | Limited |
| Brass | No | Limited |
| Copper Alloy | No | Limited |
| Steel | No | Limited |
| Titanium | Limited | Limited |
Specifications and drawing call-outs
Citric passivation
- ASTM A967 — Standard Specification for Chemical Passivation Treatments for Stainless Steel Parts
- AMS 2700 — Passivation of Corrosion Resistant Steels
PASSIVATE PER ASTM A967, CITRIC 2; VERIFY BY HIGH-HUMIDITY TEST; NO VISIBLE ETCHING, PITTING, OR STAINING
Electropolishing
- ASTM B912 — Standard Specification for Passivation of Stainless Steels Using Electropolishing
ELECTROPOLISH STAINLESS STEEL PER ASTM B912; REMOVE 0.0002–0.0005 IN PER SURFACE; FINAL Ra 0.4 µm MAX; MASK THREADS
Citric passivation vs Electropolishing — frequently asked
What is the difference between Citric passivation and Electropolishing?
Citric Acid Passivation and Electropolishing are both passivation & electropolishing finishes; electropolishing resists corrosion better. Citric passivation is the lower-cost option ($). Electropolishing is the thinner coating (removes 5–25 µm), so it disturbs tight fits less.
When should I use Citric passivation instead of Electropolishing?
Conversely: choose Electropolishing when smoothing is required.
Is Citric passivation or Electropolishing cheaper?
Citric passivation is the lower-cost finish ($ against $$$ for Electropolishing) among the finishes FabDigit quotes. Both are priced per part with a lot minimum; the exact figure appears on the instant quote once the part is uploaded.