dielectric reaction of stainless to aluminum ?

[stevenj]

I am looking for used bow rails for my aluminum starcraft, while talking to a person who has some he stated that I may need to stay with aluminum. and not stainless due to reaction between the different metals.

Any input on this from experience. boat in fresh water only.

Thanks Steve

 

[woosterken]

Re: dielectric reaction of stainless to aluminum ?

what would happen if you took an old inter tube and made a gasket for where the rails touch the boat?

what part of n.e.ohio? I am in wooster and go to portage lakes

woosterken

 

[dingbat]

Re: dielectric reaction of stainless to aluminum ?

Aluminum and Stainless (depends on actual type of stainless) are not the best of friends. Apply any type of a voltage potential or mositure to the connection and you could have a real mess.

Take a look at this list. The closer the better. The reactivity of the metals decreases the closer they are in the list.

Metal reactions list
--------------------------------------------
Magnesium
Mg alloy AZ-31B
Mg alloy HK-31A
Zinc (hot-dip, die cast, or plated)
Beryllium (hot pressed)
Al 7072 clad on 7075
Al 2014-T3
Al 1160-H14
Al 7079-T6
Cadmium (plated)
Uranium
Al 218 (die cast)
Al 5052-0
Al 5052-H12
Al 5456-0, H353
Al 5052-H32
Al 1100-0
Al 3003-H25
Al 6061-T6
Al A360 (die cast)
Al 7075-T6
Al 6061-0
Indium
Al 2014-0
Al 2024-T4
Al 5052-H16
Tin (plated)
Stainless steel 430 (active)
Lead
Steel 1010
Iron (cast)
Copper (plated, cast, or wrought)
Nickel (plated)
Chromium (Plated)
Tantalum
AM350 (active)
Stainless steel 310 (active)
Stainless steel 301 (active)
Stainless steel 304 (active)
Stainless steel 430 (active)
Stainless steel 410 (active)
Stainless steel 17-7PH (active)
Tungsten
Niobium (columbium) 1% Zr
Brass, Yellow, 268
Uranium 8% Mo.
Brass, Naval, 464
Yellow Brass
Muntz Metal 280
Brass (plated)
Nickel-silver (18% Ni)
Stainless steel 316L (active)
Bronze 220
Copper 110
Red Brass
Stainless steel 347 (active)
Molybdenum, Commercial pure
Copper-nickel 715
Admiralty brass
Stainless steel 202 (active)
Bronze, Phosphor 534 (B-1)
Monel 400
Stainless steel 201 (active)
Carpenter 20 (active)
Stainless steel 321 (active)
Stainless steel 316 (active)
Stainless steel 309 (active)
Stainless steel 17-7PH (passive)
Silicone Bronze 655
Stainless steel 304 (passive)
Stainless steel 301 (passive)
Stainless steel 321 (passive)
Stainless steel 201 (passive)
Stainless steel 286 (passive)
Stainless steel 316L (passive)
AM355 (active)
Stainless steel 202 (passive)
Carpenter 20 (passive)
AM355 (passive)
A286 (passive)
Titanium 5A1, 2.5 Sn
Titanium 13V, 11Cr, 3Al (annealed)
Titanium 6Al, 4V (solution treated and aged)
Titanium 6Al, 4V (anneal)
Titanium 8Mn
Titanium 13V, 11Cr 3Al (solution heat treated and aged)
Titanium 75A
AM350 (passive)
Silver
Gold
Graphite

 

[stevenj]

Re: dielectric reaction of stainless to aluminum ?

Ken I am in Elyria, I have a sister that lives in Wooster. I used to do refrigeration service work at the Rubbermaid plant 20 years ago.

Dingbat, Thanks for the list, how do I determin what aluminum the boat is ?
and it may be near impossible to determin rail construction,NO? I am no matalurgist by any stretch of the imagination.

Thanks again

 

[dingbat]

Re: dielectric reaction of stainless to aluminum ?

Most aluminum boats are made from 50XX aluminum.

The type of stainless used in the railing relates to its quality. The lower cost rails, typically used on ?freshwater? and price point boats, are typically 304 stainless. The "high quality railing used in saltwater and the better quality boats is 316 stainless.

Both these types of stainless are passivated so you?re pretty far down the less from any of the aluminum. There are ways get around the problem but it wouldn?t be a cheap. I personally would stick with aluminum to minimize problems down the road.

 

[alumi numb]

Re: dielectric reaction of stainless to aluminum ?

starcraft used stainless screws but the pop rivets are aluminum.
i cleaned up and reused the screws.
put them in vinegar for a couple of weeks and came out nice.

 

[mike343]

Re: dielectric reaction of stainless to aluminum ?

The rubber insulator would be a good idea as long as the SS screw didn't touch the aluminum hull.

 

[Ned L]

Re: dielectric reaction of stainless to aluminum ?

Pads or disks cut from a plastic milk jug (or something similar) is all you need to isolate the railing iself, then there is the fastening issue that needs to be worked around.

 

[mikeneal]

Re: dielectric reaction of stainless to aluminum ?

You can buy delrin washers from McMaster Carr.

 

[This_lil_fishy]

Re: dielectric reaction of stainless to aluminum ?

You can also purchase aluminum machine screws from a good fastener supplier, they don't have very high tensile strength though. The gasket idea is best, we use it on our doors to seperate them from structural steel when needed. Although we also use stainless steel screws, the corrosion isn't normally near the screws but at the base of the doors where they sit in salt all winter...


Ian