[TowerTalk] Al-to-Al

Grant Saviers grants2 at pacbell.net
Fri Feb 16 12:22:22 EST 2018


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 at 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 at 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 at contesting.com] On Behalf Of Bill M
>>> Sent: Thursday, February 15, 2018 4:24 PM
>>> Cc: towertalk at 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 at 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 at contesting.com] On Behalf Of john at kk9a.com
>>>> Sent: Thursday, February 15, 2018 7:17 AM
>>>> To: towertalk at 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 at 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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