Interwar USAAC Question ?

[Corsairfoxfouruncle]

Hello does anyone know if late 30’s USAAC NMF aircraft have a protective anti-corrosion coat ? Im building this down in the Maritime patrol build.  

This is a B-18A With the 27th Reconnaisance squadron. They operated out of Puerto Rico in 1939 on Neutrality Patrol. Im just thinking with the Hot humid climate ? Wouldn't they need some sort of corrosion control, since they are obviously unpainted ? Any help is very much appreciated. Thank you in advance. 

 

Dennis

[Roger Holden]

6 hours ago, Corsairfoxfouruncle said:

Hello does anyone know if late 30’s USAAC NMF aircraft have a protective anti-corrosion coat ?

No, around the mid-30s they started using 'clad' alloys (Hence trade name 'Alclad').  These had a layer of pure Aluminium deposited on the surface for corrosion resistance (could also be buffed to a mirror finish).  The earlier, non-clad alloys (such as those used for example, on the Boeing 247), had to be anodised or primed and painted for corrosion resistance.

[Tweener]

It will be a month or so before I have access to the book, but I have one by Bell with a section that discusses this. I'll do my best to remember to give it a look. I imagine it will be too late by then, but it's more knowledge either way.

 

If nothing else, I believe Dana Bell has an account here, and if he doesn't have the answer I would be surprised if anyone did.

 

Best of luck,

Tweener

[Tweener]

So the book doesn't have as much information as I remembered it having, but @Roger Holden seems to be correct. The only difference I could find was that the Alclad layers weren't pure aluminum, but vastly closer to pure than the airframe itself.

[VH-USB]

49 minutes ago, Tweener said:

So the book doesn't have as much information as I remembered it having, but @Roger Holden seems to be correct. The only difference I could find was that the Alclad layers weren't pure aluminum, but vastly closer to pure than the airframe itself.

As Roger stated, Alclad is a 'clad' alloy, an inner layer of aluminum alloy with an other layer of pure aluminum to resist corrosion:

https://en.wikipedia.org/wiki/Alclad

http://naca.central.cranfield.ac.uk/reports/1927/naca-tn-259.pdf

The outer layer(s) were, indeed, pure aluminum.

Alclad was a big improvement over the earlier Duralumin which had corrosion problems.

 

Tim

[Tweener]

2 minutes ago, VH-USB said:

As Roger stated, Alclad is a 'clad' alloy, an inner layer of aluminum alloy with an other layer of pure aluminum to resist corrosion:

https://en.wikipedia.org/wiki/Alclad

http://naca.central.cranfield.ac.uk/reports/1927/naca-tn-259.pdf

The outer layer(s) were, indeed, pure aluminum.

Alclad was a big improvement over the earlier Duralumin which had corrosion problems.

 

Tim

Now that I actually use my brain, I can see that when it was 1-2 % pure aluminum, it is referring to an outer layer as opposed to an amount within the overall alloy.