Anodizing, conversion & passivation · finish comparison
Boric-Sulfuric Acid Anodizing Type IC vs Chromic Acid Anodizing Type I
Boric-Sulfuric Acid Anodizing Type IC and Chromic Acid Anodizing Type I are both anodizing & conversion coatings finishes; type I anodize is the lower-cost option ($$$).
Boric-Sulfuric Acid Anodizing Type IC
Anodizing & conversion coatings · $$$
Boric-sulfuric acid anodizing is a thin aerospace aluminum anodize recognized as MIL-A-8625 Type IC.
Chromic Acid Anodizing Type I
Anodizing & conversion coatings · $$$
Type I and low-voltage Type IB chromic-acid anodizing form thin, corrosion-resistant oxide on aluminum with less fatigue penalty than thick sulfuric anodize.
When to choose which
Choose BSA anodize
Choose BSA anodize when a non-chromic aerospace thin anodize is approved.
- Typical 2.5–7.5 µm thickness limits buildup
- Avoids chromic acid in the anodizing bath
- Lower fatigue effect than thick Type II or Type III
Choose Type I anodize
Choose Type I anodize when the legacy chromic process is mandatory.
- Thin 0.5–7.5 µm oxide limits dimensional change
- Lower fatigue debit than thick sulfuric or hard anodize
- Good corrosion protection after sealing
What the numbers say
- Type I anodize is the lower-cost option ($$$).
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 | BSA anodize | Type I anodize |
|---|---|---|
| Corrosion resistance | 71 Very good | 71 Very good |
| Surface hardness / wear | 52 Fair | 49 Fair |
| Cosmetic quality | 30 Low | 28 Low |
| Lubricity | 18 Low | 18 Low |
| Cost | 50 $$$ | 48 $$$ |
Key numbers
| Property | BSA anodize | Type I anodize |
|---|---|---|
| Thickness | 3–8 µm | 0.5–7.5 µm |
| Surface hardness | 180–350 HV | 150–300 HV |
| Salt-spray test duration | 336 h | 336 h |
| Max service temperature | 80 °C | 80 °C |
| Electrical | Insulating | Insulating |
| Colours | natural gray | natural gray |
| Relative cost | Premium ($$$) | Premium ($$$) |
| Added lead time | 5–10 working days | 5–10 working days |
| RoHS | Compliant | Conditional |
| Instant quote | On request | On request |
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 | BSA anodize | Type I anodize |
|---|---|---|
| Aluminum | Yes | Yes |
| DMLS / SLM | With care | With care |
Specifications and drawing call-outs
BSA anodize
- MIL-A-8625 — Anodic Coatings for Aluminum and Aluminum Alloys
BORIC-SULFURIC ACID ANODIZE PER MIL-A-8625 TYPE IC CLASS 1, SEALED; MASK ELECTRICAL BONDING SURFACES
Type I anodize
- MIL-A-8625 — Anodic Coatings for Aluminum and Aluminum Alloys
CHROMIC ACID ANODIZE PER MIL-A-8625 TYPE IB CLASS 1, SEALED; MASK ELECTRICAL BONDING SURFACES
BSA anodize vs Type I anodize — frequently asked
What is the difference between BSA anodize and Type I anodize?
Boric-Sulfuric Acid Anodizing Type IC and Chromic Acid Anodizing Type I are both anodizing & conversion coatings finishes; type I anodize is the lower-cost option ($$$).
When should I use BSA anodize instead of Type I anodize?
Choose BSA anodize when a non-chromic aerospace thin anodize is approved. Conversely: choose Type I anodize when the legacy chromic process is mandatory.
Is BSA anodize or Type I anodize cheaper?
Type I anodize is the lower-cost finish ($$$ against $$$ for BSA anodize) 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.
Do BSA anodize and Type I anodize protect equally against corrosion?
On paper, yes: both are rated 336 h in neutral salt spray (ASTM B117 or the qualification hours of the governing specification). In service the difference comes from sealing, thickness class and the substrate alloy rather than from the choice between the two.