Corrosion problems with new Airstreams

[Fenghuang]

Originally Posted by longdog

It's a 5 pound solid zinc anode. I think it will last a while.

Thanks for the link to marine zinc anodes. Would a marine magnesium anode work as well as or better than zinc as it is more anodic?

[Moflash]

It just seems upon close inspection that our trailers seem to have filform in the areas where steel screws fasten parts to the aluminum structure ie taillight bezels,grab handles,clearance lights,wheel trim,rear bumper etc.
And on electrified components it seems to get bad quick (tail light housings,clearance lights)c.Could it bee that stringing 12 volt wiring thru out a aluminum on steel grounding structure and energizing it create a problem?
When I changed out my 15 inch wheels for 16's my trailer had less than 800 miles and I noticed filform on the aluminum wheels around every lug nut hole in a perfect circle that each hole had the exact same pattern of corrosion (thats 20 holes).My trailer has never been near the ocean and is hand washed and dried before during and after use(top and bottom),hand waxed at least 3 times a year with a ultra high grade polymer wax (I even wax the frame)and stored indoors when not in use on a plastic covered floor so that moisture does not wick up from the ground.Yes I use Boeshield and Corrosion X but It still forms This leads me to believe alot of this corrosion is caused by electrolysis.Along the seams where the two pieces of aluminum sheeting meet is also a problem area for our trailers and everyone points the finger at sloppy handling of the sheets chipping off the clear coat.But could it actually be the rivet stems being a different metal composition are creating a positive vs negative charge and thus contaminating the area and allowing electrolysis to work its magic and gain a quick foothold in the areas where the clear coat has been chipped.And plcing the structure next to salt water would amplify and speed up the process. Food for thought , just a theory.....
Any degreed electrical engineers out there I would like to here what you have to say.

[Howard L.]

Originally Posted by ROBERT CROSS

Mo,

That's probably because they were assembled with a modicum of care.... .......and don't use pre-coated Alcoa panels.

Bob

Bob, I hate to ask this of you again, but I believe you have a past post with an Internet link that explains the different types of corrosions; Filiform, galvanic, etc. I think several of us, maybe most of us, are getting messed up on what types of corrosion and it's possible cause, we're dealing with in some of these issues. Filiform, we know we have; galvanic, it will show sooner or later also, but why and from what?. Electrolysis, and sacrificial zincs for an AL trailer sitting in air???

Thanks Howard

[DMT]

Originally Posted by idroba

I will admit that I have not read all 117 pages of posts on this thread, but has anyone used the Dupont "Pro-Fusion color Scratch Repair Stick" to cover the cut edges of the aluminum where the corrosion seems to start. They are available in packs of 3 for about $12 at Costco, and are listed as a clear coat scratch repair system. I was wondering if they might be a good way to seal the visible cut edges on my new 2014 FC 20. The ones I have in mind are around the panel which has the rear window in it. It looks to be cut out of a sheet of metal and just riveted in place on the surface of the rear segments. The cut edges are exposed. If not, what does the group recommend for those edges?

I have. The application works quite well although only time will tell if it is durable. Much easier than a spray can or a brush, and economical as well.

[DMT]

Originally Posted by Howard L.

Bob, I hate to ask this of you again, but I believe you have a past post with an Internet link that explains the different types of corrosions; Filiform, galvanic, etc. I think several of us, maybe most of us, are getting messed up on what types of corrosion and it's possible cause, we're dealing with in some of these issues. Filiform, we know we have; galvanic, it will show sooner or later also, but why and from what?. Electrolysis, and sacrificial zincs for an AL trailer sitting in air??? Thanks Howard

Galvanic corrosion needs dissimilar metals and a conductive fluid connecting the two to allow material transfer. An Airstream sitting in air does not have that.

[idroba]

Originally Posted by DMT

I have. The application works quite well although only time will tell if it is durable. Much easier than a spray can or a brush, and economical as well.

Thank you for your comment. I guess I will try it out too. No idea if it will do any good, because there is no "control" test with two trailers in identical situations, one with and one without the scratch pen clear coat repair system being used on it.

That is always a big issue with one off testing. You never know if the success (if you seem to have it) is because of what you did or if the problem would not have shown up on your unit had you done nothing at all.

One can report failure though.

[DMT]

Originally Posted by idroba

Thank you for your comment. I guess I will try it out too. No idea if it will do any good, because there is no "control" test with two trailers in identical situations, one with and one without the scratch pen clear coat repair system being used on it. That is always a big issue with one off testing. You never know if the success (if you seem to have it) is because of what you did or if the problem would not have shown up on your unit had you done nothing at all. One can report failure though.

Unfortunately my testing conditions are severe as I live on the coast of the North Atlantic. So if it works for me it should work for anyone. I'll update the thread in the spring regarding how the Costco clear coat pens made out.

[Moflash]

Originally Posted by DMT

Galvanic corrosion needs dissimilar metals and a conductive fluid connecting the two to allow material transfer. An Airstream sitting in air does not have that.

A Airstream sitting in indoor air does not have that.
But with aluminum and dissimilar metals that are exposed to water in the form of rain or condensation or 80% or higher humidity this would qualify as a electrolyte (or conductive fluid).Which in turn would lead to galvanic corrosion I believe according to what I have read.

[Moflash]

Quality engineering and design requires an understanding of material compatibility. Galvanic corrosion (some times called dissimilar metal corrosion) is the process by which the materials in contact with each other oxidizes or corrodes. There are three conditions that must exist for galvanic corrosion to occur. First there must be two electrochemically dissimilar metals present. Second, there must be an electrically conductive path between the two metals. And third, there must be a conductive path for the metal ions to move from the more anodic metal to the more cathodic metal. If any one of these three conditions does not exist, galvanic corrosion will not occur. Often when design requires that dissimilar metals come in contact, the galvanic compatibility is managed by finishes and plating. The finishing and plating selected facilitate the dissimilar materials being in contact and protect the base materials from corrosion.

For harsh environments, such as outdoors, high humidity, and salt environments fall into this category. Typically there should be not more than 0.15 V difference in the "Anodic Index". For example; gold silver would have a difference of 0.15V being acceptable.
For normal environments, such as storage in warehouses or non-temperature and humidity controlled environments. Typically there should not be more than 0.25 V difference in the "Anodic Index".
For controlled environments, such that are temperature and humidity controlled, 0.50 V can be tolerated. Caution should be maintained when deciding for this application as humidity and temperature do vary from regions

METALLURGICAL CATEGORY

ANODIC INDEX (V)

Gold, solid and plated, Gold-platinum alloy

0.00

Rhodium plated on silver-plated copper

0.05

Silver, solid or plated; monel metal. High nickel-copper alloys

0.15

Nickel, solid or plated, titanium an s alloys, Monel

0.30

Copper, solid or plated; low brasses or bronzes; silver solder; German silvery high copper-nickel alloys; nickel-chromium alloys

0.35

Brass and bronzes

0.40

High brasses and bronzes

0.45

18% chromium type corrosion-resistant steels

0.50

Chromium plated; tin plated; 12% chromium type corrosion-resistant steels

0.60

Tin-plate; tin-lead solder

0.65

Lead, solid or plated; high lead alloys

0.70

Aluminum, wrought alloys of the 2000 Series

0.75

Iron, wrought, gray or malleable, plain carbon and low alloy steels

0.85

Aluminum, wrought alloys other than 2000 Series aluminum, cast alloys of the silicon type

0.90

Aluminum, cast alloys other than silicon type, cadmium, plated and chromate

0.95

Hot-dip-zinc plate; galvanized steel

1.20

Zinc, wrought; zinc-base die-casting alloys; zinc plated

1.25

Magnesium & magnesium-base alloys, cast or wrought

1.75

Beryllium

1.85

[dkottum]

The sacrificial anode is a red herring, but this thread is very useful in providing various successful treatment and repair methods.

[Edistobob]

Originally Posted by dkottum

The sacrificial anode is a red herring, but this thread is very useful in providing various successful treatment and repair methods.

So, all things considered, would the use of a sacrificial anode be completely pointless for someone in the sort of climate I have? It would definitely qualify as "harsh" according to the earlier post. We live at the edge of a salt marsh in hot, humid coastal South Carolina, and the Airstream is parked outside, probably about 30 feet from the edge of the marsh. If there is any chance at all that it would do some good, it certainly is an inexpensive item to try and I am assuming it could not hurt anything.

Comments?

[dkottum]

It's a distraction from useful methods. Use it you want but don't depend on it.

[Moflash]

doug
I am curious what knowledge or field of science are you basing your above statements on? Please elaborate.

The purpose of this thread is for discussing the corrosion problems for new Airstreams and it would be nice to know the cause is and not how to patch or repair this problem or spreading a paraffin wax all over a $45,000-$100,000 travel trailer.

I dont buy the "Its all how you maintain your Airstream or it only happens to people who live or travel next to the ocean story in regards to the corrosion issue.This may accellerate the corrosion but is definitely not the cause from what I see.

[DMT]

I agree with Doug.

If anodes could be of any benefit in a "surface" situation to prevent corrosion then automakers would have taken that road instead of hot dip galvanizing and undercoating. Same for the aerospace industry.

The two stumbling blocks to getting the galvanic circuit flowing I see are the presence of protective coatings and the extremely low standing time in the electrolyte. It's just not wet enough for long enough. I would not worry about galvanic corrosion on an Airstream.

[John&Vicki]

The hillbilly anti-corrosion method: Wire an anode, hang a bucket full of water off of the rear bumper, drop the anode into the bucket. Old lead sinkers work good.

Poppy

[ROBERT CROSS]

Originally Posted by Howard L.

Bob, I hate to ask this of you again, but I believe you have a past post with an Internet link that explains the different types of corrosions; Filiform, galvanic, etc. I think several of us, maybe most of us, are getting messed up on what types of corrosion and it's possible cause, we're dealing with in some of these issues. Filiform, we know we have; galvanic, it will show sooner or later also, but why and from what?. Electrolysis, and sacrificial zincs for an AL trailer sitting in air???

Thanks Howard

No problem Howard.

There are two good sites....

alumatter Click on the links on the left side.

Kennedy Space Center...

Bob

[Bluto]

Originally Posted by Moflash

doug
I am curious what knowledge or field of science are you basing your above statements on? Please elaborate.

The purpose of this thread is for discussing the corrosion problems for new Airstreams and it would be nice to know the cause is and not how to patch or repair this problem or spreading a paraffin wax all over a $45,000-$100,000 travel trailer.

I dont buy the "Its all how you maintain your Airstream or it only happens to people who live or travel next to the ocean story in regards to the corrosion issue.This may accellerate the corrosion but is definitely not the cause from what I see.

The way I see it, some trailers get it, and some don't. It seems it comes down to 2 things, enviroment and upkeep.

[dkottum]

Originally Posted by Bluto

The way I see it, some trailers get it, and some don't. It seems it comes down to 2 things, enviroment and upkeep.

Exactly.

[John&Vicki]

Especially when there is salt present, either through roads or coastal environments.

Poppy

[dkottum]

Originally Posted by Birdmaestro

Especially when there is salt present, either through roads or coastal environments.

Poppy

That's why we need a barrier between the exposed metal edges, rivet holes, fittings and the environment.

I know of nothing better than Corrosion X or Boeshield T9, applied often enough to maintain the barrier. It's an easy measure to do, and at least somewhat effective.

That does not preclude the need to wash the trailer after exposure.