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topic 18759

Fasteners for aluminum structure

A discussion started in 2002 but continuing through 2019


I'm building a project that uses aluminum frame fastened to a aluminum sub-frame. Assembly we want to use a self-drilling screw. What material would fasteners need to be constructed from to prevent galvanic or electrolysis?

Lovell Reed
- Orlando, Florida

simultaneous 2002

A. Cadmium Plating with chromate is the old fashioned answer and there is at least one job plating house left in Florida that still does Cadmium.

robert probert
Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina


A. Traditionally such screws were cadmium plated for galvanic compatibility with aluminum. But cad plated hardware is hard to get these days and reserved for special situations because it is a biocumulative poison like lead and mercury. If the structure is a truly significant and critical one, you can get hardware that is coated with aluminum by electroplating or Ivadizing. Otherwise, standard stainless steel or galvanized hardware should be good enough.

Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha


A. Dear Mr. Reed,

We received best results with heat-treated screws, electroplated with 8-12 µm. Zinc/Nickel (about 13 % Nickel), black-passivated (chromium 6 free) and provided with a PTFE based dry-lubricant.


- Netherlands


A. Tin - zinc is probably the closest match for cadmium plating. Unless it a particularly nasty environment, 18-8 stainless screws are a possibility. SS would be a poor choice in a maritime environment.

James Watts
- Navarre, Florida

How to fasten aluminum sculpture to marble base for exterior location

September 22, 2019 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. How to fasten aluminum sculpture to marble base for exterior location, Marble will be horizontal surface, and exposed to the weather.

Craig VanderHoff
- comstock park, Michigan

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