Galvanic corrosion chart.
When two different metals touch in the presence of water, the less noble one corrodes faster. The fastener should be the same metal as the parts or more noble than them: a stainless screw in aluminium is acceptable with care, a zinc-plated screw in stainless sheet loses its plating quickly. General guidance, not a design rule.
Reviewed 11 Nov 2026 · Based on Fastenal Engineering, Corrosion & Corrosion Resistance (rev. 2009-03-04): plating compatibility chart and galvanic series; NIH Office of Research Facilities Technical Bulletin 161 (June 2026): mitigation hierarchy, citing ASTM G82 and MIL-STD-889D · Report an error
Questions on this?
| Base metal ↓ / fastener → | Zinc-plated or galvanized steel | Aluminium and aluminium alloys | Carbon steel and cast iron | Brass, copper, bronze, Monel | Martensitic stainless 410 | Austenitic stainless 302/304, 303, 305 (A2) |
|---|---|---|---|---|---|---|
| Zinc-plated or galvanized steel | 1 | 2 | 2 | 3 | 3 | 3 |
| Aluminium and aluminium alloys | 1 | 1 | 2 | 3 | Never | 2 |
| Carbon steel and cast iron | 1, 4 | 1 | 1 | 3 | 3 | 2 |
| Brass, copper, bronze, Monel | 1, 4, 5 | 1, 5 | 1, 5 | 1 | 1 | 2 |
| Martensitic stainless 410 | 1, 4, 5 | 1, 5 | 1, 5 | 1 | 1 | 1 |
| Austenitic stainless 302/304, 303, 305 (A2) | 1, 4, 5 | 1, 5 | 1, 5 | 1, 5 | 1 | 1 |
| Order | Metal or alloy |
|---|---|
| 1 | Magnesium and magnesium alloys |
| 2 | Zinc |
| 3 | Aluminium 1100 |
| 4 | Cadmium |
| 5 | Aluminium 2024-T4 |
| 6 | Iron and steel |
| 7 | Lead |
| 8 | Tin |
| 9 | Nickel (active) |
| 10 | Inconel nickel-chromium alloy (active) |
| 11 | Hastelloy alloy C (active) |
| 12 | Brasses (Cu-Zn alloys) |
| 13 | Copper |
| 14 | Bronzes (Cu-Sn alloys) |
| 15 | Copper-nickel alloys |
| 16 | Monel (70Ni-30Cu) |
| 17 | Nickel (passive) |
| 18 | Inconel (80Ni-13Cr-7Fe) |
| 19 | 304 stainless steel (passive) |
| 20 | 316 stainless steel (passive) |
| 21 | Hastelloy alloy C (passive) |
| 22 | Silver |
| 23 | Titanium |
| 24 | Graphite |
| 25 | Gold |
| 26 | Platinum |
Reference values, not a design.
Values are the nominal figures of the cited standards, or calculated from them where marked. The governing standard and your drawing always take precedence.
Questions buyers ask.
Can I use stainless steel bolts in aluminium?
The published chart rates austenitic stainless (A2) fasteners in aluminium as marginally increasing the aluminium's corrosion. It is common practice, but in wet or coastal service isolate the contact with non-conductive washers and sleeves, or a sealant, so water cannot bridge the two metals.
Can I use zinc-plated or galvanized bolts in stainless steel?
Not where the joint gets wet. The chart shows the zinc coating is rapidly consumed against stainless, brass or copper, leaving bare steel that then corrodes. Use stainless fasteners in stainless parts.
How do I stop galvanic corrosion at a bolted joint?
In order of preference: choose compatible metals; break the electrical path with non-conductive washers, sleeves or gaskets; apply a barrier coating or sealant to the contact faces (and maintain it); and keep the joint drained. A small anode against a large cathode corrodes fastest, so make the fastener the more noble metal.
Does galvanic corrosion happen indoors?
It needs an electrolyte. In dry, heated interiors the effect is usually negligible; condensation, washdown, rain and salt spray are what drive it.
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