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Re: [TowerTalk] Al-to-Al

To: Kim Elmore <cw_de_n5op@sbcglobal.net>, Keith Dutson <kdutson@sbcglobal.net>
Subject: Re: [TowerTalk] Al-to-Al
From: Grant Saviers <grants2@pacbell.net>
Date: Fri, 16 Feb 2018 09:22:22 -0800
List-post: <mailto:towertalk@contesting.com>
As with most issues, "it depends". Passivation of SS is a process used to make SS alloys less chemically reactive. SS is an alloy of Cr, Ni, Fe and other metals & C in a matrix and if the Fe is removed at the surface the reactivity (EMF differential) is reduced. This also makes the SS less likely to show rust pits. Fe and Al are far apart on the EMF scale so passivation is very desirable if SS is used to fasten Al. ie Al "sacrifices" to Fe.

The SS alloy also makes a big difference - 18-8 is the most common fastener alloy. 316 is a better alloy choice and 316L is used when welding marine structures since it has less carbon, which in the actual weld promotes free iron and therefore rust. Better, generally available, but more expensive. The next step in corrosion resistance is Monel, mostly nickel and now the fasteners are getting really expensive, but Ni is closer in EMF to Al.

The EMF differential of Zn vs Al is the lowest of any practical metal assembly with Al. So Zn is very compatible with Al even though the reaction is one to slightly sacrifice the Al. Zincate is a Zn plating process that prepares Al for further plating - copper, nickel, etc. The Zn bonds very well to Al, which otherwise is very hard to plate either with electrolytic or electroless processes.

The Zn particles in the popular corrosion inhibitors I think are more of "compatible ball bearings" than corrosion inhibition. Beam elements I've disassembled after 8 years protected with Penetrox came apart pretty easily. I don't use Cu carrying protection on Al to Al per the manufacturer's recommendations.

Also, hot dip galvanized fasteners are a good choice for larger bolt sizes. Available 1/4-20 and up, they are cheaper than SS, don't gall, and are very compatible with Al.

Grant KZ1W



On 2/15/2018 19:52 PM, Kim Elmore wrote:
 From this thread, I learned that stainless steel and aluminum are a corrosive 
combination. I hadn’t heard this before.

I’ve known that copper and aluminum are a corrosive combination and so the Jet 
Lube SS-30 surprises me. But I also wonder about zinc (the main component of NoAlOx, 
OxGard, and Penetrox) and aluminum. Is that truly a combination that plays well 
together?

Kim N5OP

"People that make music together cannot be enemies, at least as long as the music 
lasts." -- Paul Hindemith

On Feb 15, 2018, at 18:44, Kim Elmore <cw_de_n5op@sbcglobal.net> wrote:

I asked the question to make sure something was needed for Al-to-Al and it seems it is 
truly is. Long ago, I was told that Al-to-Al was best dry because galvanic corrosion 
couldn’t

When I was In CO, I used some stuff called OxGard because it was supplied with 
an antenna. It seemed to work well there, but CO is very dry. OxGard has a 
petroleum grease containing graphic and zinc particles. After about 10 y in CO, 
everything seemed fine and when I took the antennas apart to move to OK, the 
grease was still greasy. I used it when I reassembled the antennas here. But, I 
always wondered if the stuff was truly necessary.

Kim N5OP

"People that make music together cannot be enemies, at least as long as the music 
lasts." -- Paul Hindemith

On Feb 15, 2018, at 16:45, Keith Dutson <kdutson@sbcglobal.net> wrote:

May have something to do with weather conditions.  I noticed Penetrox seems to 
dry out quicker here.

-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Bill M
Sent: Thursday, February 15, 2018 4:24 PM
Cc: towertalk@contesting.com
Subject: Re: [TowerTalk] Al-to-Al

We found when we took older antennas down where Penetrox was used were corroded 
together or extremely hard to separate. We went to Noalux 30 years ago and 
haven’t looked back.
Bill W2CQ

On Feb 15, 2018, at 9:05 AM, Keith Dutson <kdutson@sbcglobal.net> wrote:

Cannot find Noalox here in these stores in Houston.  Penetrox is available, and 
I keep a supply in the shack for general use.  Seems to be pretty much 
identical to Noalox for my use.

73, Keith NM5G

-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of 
john@kk9a.com
Sent: Thursday, February 15, 2018 7:17 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Al-to-Al

Noalox seems to be more available at the big box stores, I wonder why Penetrox 
became popular with amateur antenna builders.

John KK9A


To:    towertalk@contesting.com
Subject:    Re: [TowerTalk] Al-to-Al
Date:    Wed, 14 Feb 2018 16:09:29 -0500

We’ve tried pretty much everything in our salt air environment of South 
Florida. Most here use Noalux successfully over the past 30+ years.
Bill W2CQ

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