Marine & Offshore Fasteners | 316/A4 Stainless and Heavy-Duty Dacromet
Fasteners for ships, seawater lines, deck machinery and port facilities: 316/A4 stainless against marine-atmosphere chloride pitting (PREN 24-26, a full environment class above 304), plus Dacromet (500-1000 h+, hydrogen-free) or hot-dip (1000 h+) carbon steel, with crevice-corrosion and contamination-control guidance.
Key Technical Challenges
Marine air is chloride-rich; 304 pits through on the coast - seaside service requires 316
Oxygen-starved crevices under nuts and washers cannot re-passivate, so even stainless rusts inside the gap
Embedded carbon-steel fines cause foreign rust that gets misread as a material defect
Seawater systems above 60°C under stress put austenitic stainless at stress-corrosion-cracking risk
Xin Rui Da Fastener Solutions
316/A4 stainless sets (16Cr-10Ni-2-3Mo): one environment class above 304 against chloride pitting; anti-seize on critical joints against galling and crevice attack
Carbon steel routed through Dacromet (500-1000 h+, hydrogen-free, 4-10 um so standard nuts fit) or HDG (1000 h+, nuts oversize 0.2-0.4 mm)
Escalation advice for hot chlorided duty: duplex 2205 (PREN about 33-35) on special order to avoid SCC
VCI bag + desiccant four-layer packing for stainless too - sea humidity attacks stainless without protection
Technical Parameters
| Stainless Basis | A4-70 / A4-80 · 316/316L · PREN 24-26 |
| Carbon Steel Finish | Dacromet 500-1000 h+ · HDG 1000 h+ |
| SCC Threshold | >60°C chlorided water under stress |
| Escalation | Duplex 2205 PREN ~33-35 (special order) |
| Packing | VCI bag + desiccant + IPPC crate |
Frequently Asked Questions
304 scores PREN 18-20 without molybdenum; 316 with 2-3% Mo scores 24-26, about 35% higher - one full environment class more pitting margin. 304 pits through in coastal salt spray; 316 plus periodic fresh-water rinsing is the working combination.
They can. Salt-laden humidity can pit even 304/316 - stainless is not a get-out-of-jail card. Keep the same VCI bag + desiccant inner packing, and verify by checking the desiccant on arrival.
Above 60°C with chlorides under stress, austenitic 304/316 face stress-corrosion cracking; escalate to duplex 2205 or nickel alloys, assessed against concentration - send the duty conditions for our engineers to verify.
Get a Fastening Solution for This Industry
Send the joint duty — load, media, temperature and size — and our engineers reply with class selection and quotation within 24 hours.