Tef-Gel experience with Galvanized fasteners 1

[sunstructures]

Hello,
It has been recommended to me to use Ultra Safety Systems' Tef-Gel in a connection involving 6061-T6 Aluminum beams and channels and Type 316 stainless bolt assemblies to inhibit galvanic corrosion. However, the original concept involved assembling the aluminum structure with ordinary ASTM A325 hot-dip galvanized bolts. The reason given was because the mild steel is close to the aluminum on the galvanic series, and zinc remains the most anodic component. Inert sleeves of some sort were recommended in the galvanized bolt configuration.
Will the hot-dip galvanized A325 bolts, if lubed with Tef-Gel, perform satisfactorily without additional isolation spacers or washers? Will the Tef-Gel interfere in any way with the structural performance of the connection? Also, what other products are in use that function like the Tef-Gel?
Thanks.

 

[jjdoodah]

The person that spec'd. the Galv. bolts with the Alum. didn't know what he was doing. The SS is the proper fastener. Either T304 or T316 or even 16-6 will work.
The 316 is the better for corrosion resistence. Never let carbon or Galv. parts interact with the Alum. Hope this helps.

 

[sunstructures]

Thanks for the comment. We are currently evaluating SS bolts for this installation.

With the SS bolts, will it still be necessary to use an isolation sleeve or washer under SS washer at the bolt head and nut, or would such a product as Tef-Gel sufficiently protect the dissimilar metals? The product literature states that it is being widely used by marine equipment manufacturers in SS to Al connections. Would any dielectric grease work? The Tef-Gel is supposed to remain stable in the connection, whereas grease could run out or dry out, so it seems the best choice.

 

[LuizSouza]

Sun

You can help, by your turn. What's Tef-Gel, and where I can find some literature about on internet?

 

[sunstructures]

"Tef-Gel" or "something similar" was mentioned in another thread as a means of anti-seizing or anti-galling. I did a web search and found a contact, and put in a call. I hope to be getting more specifics soon. From the Ultra Safety Systems website, at

http://www.tefgel.com

, I found the contact info and MSDS and packaging info.

Manufacturers Name: ULTRA SAFETY SYSTEMS
Address: Telephone Number for Information:
3755 Fiscal Court (561) 845-1086 / (800) 433-2628
Riviera Beach, Fl 33404

Another marine equipment related website has an illustration that shows the Tef-Gel in use as an isolation barrier between aluminum parts and SS fasteners.
Unfortunately my bookmarks seem to have disappeared from that session, so I'll have to re-post them later along with further info from the mfr.

 

[sunstructures]

Here you go...

http://www.tefgel.com.au

Also, spoke with the man himself. Mr. Morgenthaler. Looks like it will work for either galvanized or SS fasteners in contact with Al, but his recommendation of course went to SS fasteners in Al members.

Thanks for the input...

 

[sunstructures]

jjdoodah,
The recommendation to use HD galvanized structural bolts with the aluminum connections came from a water systems engineer. The recommendation is based on the mild steel being closer to the aluminum on the MIL-STD-889 galvanic corrosion sequence table than the 300 series stainless.
(URL:

http://www.eaa1000.av.org/technicl/corrosion/galvanic.htm

). The table is the galvanic series of metals in sea water from Army Missile Command Report RS-TR-67-11, "Practical Galvanic Series."

The Zinc galvanizing is more anodic than the 6061-T6 aluminum, so any corrosion would occur on the Zinc, accelerating the loss of galvanizing on the fastener. I see your points as that would lead to a rusting steel fastener. This seems completely opposite to the concept of making the anodic material the largest surface. However, the Zinc galvanizing and the underlying steel bolt that it protects are even further on the table, so the potential to lose Zinc galvfanizing is actually faster between the steel and the zinc than the aluminum and the zinc.

With Zinc being even closer to aluminum than the steels, wouldn't the rate of corrosion be very low, if at all? Zinc anodes are used for aluminum ship hulls right? And the water engineer also insisted on a dielectric isolation material between the bolts and the attached parts, which would further eliminate the possibility of galvanic corrosion.

This project is not in a marine environment, so HD galvanized bolts properly isolated from aluminum seem to be the least expensive way to join the parts together.

Since this thread is about Tef-Gel performance with HDG steel fasteners, I should mention that the Tef-Gel material, by keeping out moisture and remaining inert and non-volatile, should satisfy the requirements of eliminating the galvanic cell potential between the AL 6061 and the Zinc. Then it becomes simply an HD galvanized bolt lifespan issue.

I'm specifying stainless steel bolts with isolation on this project at this time, and plan to keep it that way, but it seems that the HDG fasteners are not a bad choice altogether for this type of project.

Another thread I have here is whether the proprietary (and expensive) Tef-Gel lubricant performs any better than white lithium grease or proprietary Lanocote as a dielectric isolator, but that's another thread.

Thanks for the discussion.