ASTM B545
Standard Specification for Electrodeposited Coatings of Tin
Specifies electrodeposited tin coatings on metallic articles for solderability, contacts, corrosion protection, anti-galling, and nitriding stop-off.
What ASTM B545 specifies
ASTM B545 covers electroplated tin of at least 99% purity and divides service into Classes A through F. Minimum thicknesses are 2.5, 5, 8, 15, 30, and 1.5 µm, with steel-specific increases to 10 µm for Class C and 20 µm for Class D. Class F is a short-term, purchaser-approved thin coating rather than the highest service level. The standard also distinguishes matte, bright, and flow-brightened appearance. Buyers should state service class, substrate, underplate, appearance, solderability retention, whisker-risk controls, significant surfaces, and hydrogen-relief requirements for high-strength steel.
ASTM B545 types and classes
Every designation the document defines, with the thickness it requires and the tests it imposes.
| Designation | Meaning | Thickness | Coating weight | Requirement / test |
|---|---|---|---|---|
Class A | Low-resistance contacts and mild protected service. | ≥ 3 µm ≥ 0.1 mil | — | Thickness and applicable contact tests. |
Class B | Solderability, anti-galling, stop-off, and similar mild service. | ≥ 5 µm ≥ 0.2 mil | — | Thickness, adhesion, and solderability when specified. |
Class C | Indoor moderate exposure and solderability retention. | ≥ 8 µm ≥ 0.31 mil | 10 µm minimum on steel. | Thickness, integrity, and solderability. |
Class D | Dampness and moderate industrial exposure. | ≥ 15 µm ≥ 0.59 mil | 20 µm minimum on steel. | Thickness, integrity, and applicable corrosion test. |
Class E | Elevated temperature, abrasion, or corrosive exposure. | 30–125 µm 1.2–4.9 mil | 30–125 µm may be required for abrasion or corrosive media. | Thickness, integrity, and specified performance. |
Class F | Short-term contact or limited shelf life, subject to purchaser approval. | ≥ 2 µm ≥ 0.06 mil | — | Thickness and purchaser-approved performance. |
Tests and the drawing call-out
Tests the document imposes
- Purity
- Local and mean thickness
- Adhesion
- Porosity and integrity
- Solderability when specified
- Hydrogen-embrittlement relief
How to cite it
Drawing call-out
TIN PLATE PER ASTM B545, CLASS <A|B|C|D|E|F>, <MATTE|BRIGHT|FLOW-BRIGHTENED>, <UNDERPLATE>Angle brackets mark the choices the drawing must make; every finish page shows a completed example.
Finishes specified to ASTM B545
ASTM B545 — frequently asked
Is Class F the most severe class?
No. Class F is the thinnest, at 1.5 µm, for short-term contact or limited shelf life. Class E covers very severe service.
Why is Class C thicker on steel?
Class C is 8 µm generally but 10 µm on steel to reduce porosity-related corrosion. Class D similarly rises from 15 to 20 µm on steel.
Should matte or bright tin be specified?
Yes. Appearance and deposit structure affect solderability and tin-whisker risk, so the purchase requirement should not leave the choice open.
ASTM B545 is copyrighted by ASTM International. This page explains the document so a drawing can be read; it does not reproduce the standard. Purchase the current edition from the publisher. Official source ↗