finishing.com logo
  HOMEFAQsBOOKSHelpWantedAdvertiseContactFORUM Letter 43834

The finishing.com Hotline -- Serious Education ... plus the most fun you can have in metal finishing

Cadmium coated bolts / nuts vs. stainless steel bolts for seawater exposure

(2007)

We are trying to determine the best / longest lasting materials for metallic hardware items (nuts, bolts, washers) in an underwater sea-water / salt water exposure (a pipe line).

Will a cadmium coated steel perform better or worse underwater than will a stainless steel material? Should the stainless steel material be coated as well?

Kenneth R. Martin
Aquatic Design & Engineering, Inc. - Oakland, Florida, USA

(2007)

Much worse. Cadmium plating 0.0005" thick, yellow chomated, may last 1 week before white rust and 1-6 months before red rust. Somewhat illegal due to toxicity.

No, use a suitable grade of stainless. For fasteners, 2205 (UNS S31803) is better than 316 with respect to strength and resistance to crevice & pitting corrosion & SCC. What is the pipeline material -- coated steel, stainless, reinforced plastic...? Galvanic compatibility may be an issue.

The best long-term material for both pipeline and hardware is probably titanium.

Ken Vlach
- Goleta, California  

Ken received a special
"Contributor of the Year" award
from finishing.com for his numerous
helpful and well researched responses


(2007)

Cadmium plated steel bolts are not suitable for seawater usage, and neither are most stainless steels. The proper choice of fastener depends a great deal on what is being joined (geometry, materials, stresses, etc.). Nickel-based alloys like MONEL K-500 or INCONEL 686 or Titanium alloys like TIMETAL 5111 are the most resistant to corrosion and offer high strength and toughness. However, if the stresses are not too high, a duplex stainless steel grade like 254SMO (UNS S31254) may be acceptable.

Toby Padfield
Automotive module supplier - Michigan

ADD a Q or A to THIS thread START a NEW THREADView This Week's HOT TOPICS

Disclaimer: It is not possible to diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous; some names may be fictitious and some recommendations may be deliberately harmful.

  If you need a product/service, please check these Directories:

JobshopsCapital Equip. & Install'nChemicals & Consumables Consult'g, Train'g, SoftwareEnvironmental ComplianceTesting Svcs. & DevicesUsed & Surplus


©1995-2015 finishing.com     -    Privacy    -    Search