Bill W G S

What is the reason that the materials in modern fighter airframes appear yellow or green?

[link=http://gizmodo.com/5021998/build-your-own-f+35-lightning-ii-fighter-jet]f35[/link]

stang

My Feedback: (1)

The aluminum is sprayed with zinc chromate to inhibit corrosion.

ChuckW

I am no expert on the subject but I believe the yellow/green is a specific kind of primer.

jetmech05

having been in corrosion control for a short time and In the Marine Corps (usually near an ocean)..nothing corrodes faster than bare aluminum...wheel wells are usally painted white..but areas of the aircraft that don't see the light of day often are indeed painted with zinc chromate

w8ye

My Feedback: (16)

This has been done on airplanes ever since they started using aluminum

TFF

It is some polyurathane or epoxy now instead of the old style zinc cromate. The new stuff really sticks.

w8ye

My Feedback: (16)

I know in old real airplanes corrosion is a real problem at the rear bottom of the fuselage in front of the formers and at the low parts of the wings. The aluminum just crumbles away.

Ram Jet

My father was a vetran of the U.S.Army Air Corps in WWII. He was a Field Service Engineer for Curtiss Wright. He told me that until the came up with zinc chromate primer it was very difficult to get paint to adhere to aluminum. Hence the puke green areas inside cockpits, wheel wells, engine bays etc.

Bill

w8ye

My Feedback: (16)

I think the green stuff is also like Ram Jet Said has an ability to somewhat combine with the surface of the aluminum to promote adhesion.

I was going to say etchant but that is not the right word.

During WW II the Japanese apparently didn't have it completely figured out for the paint peeled from their planes all the time

HighPlains

My Feedback: (1)

The aluminum sheets used in the construction of aircraft is usually 2024-T3 Alclad of different thickness. Alclad is a composite material, consisting of aluminum combined with trace amounts of copper, manganese, magnesium, and chromium to give it strength and hardness. Coating the exterior of the sheet is a very thin layer of pure aluminum, which gives it corrosion resistance, since the pure alumimum soon becomes a layer of aluminum oxide that protects the alloy below.

Some preprocess the aluminum sheets with a alodine process, or slightly etch the surface. Other methods of surface prep may just skuff the surface lightly with Scotchbrite pads. Then a final cleaning and the application of the zinc chromate with the delightful Linda Blair pea spray green tint.

This was not done to WW11 airplanes sometimes for several reasons. It added weight, but more importantly, the expected lifetime of aircraft in war was measured in tens of hours.

w8ye

My Feedback: (16)

The color varies from an almost olive drab to leaning towards yellow

jetmech05

there is zinc chromate green and there is zinc chromate yellow...green is the more often seen color...I haven't seen yellow in 25 some odd years

Bill W G S

How difficult is it to apply this zinc chromate primer? Can it be sprayed on with a standard air brush for scale applications or are the particles to big for such a device?

w8ye

My Feedback: (16)

It used to come in a rustolium spray can.

My dad had some in a paint can so apparently you could brush it.

jetmech05

Testor's Model Master paint which is not fuel proof has Zinc chromate color....you can try fuel proof clear ove that..I don't know if it'll work or not

HighPlains

My Feedback: (1)

I think that you can buy small spray cans of something close from aircraft spruce or wicks aircraft. But if you use a lot of it, you buy it by the gallon for about $200 per gallon.

Homebuilding an RV-4.

FILE IFR

In full scale they stopped using "green" I think in the mid 1950's (military).

After that the chromate "yellow" became the new color of primer/corrosion coating.... including civilian A/C.

jetmech05

I was using green in the mid 70's

496xl

I was using it up to about 3 years ago.(Green chromate)

Rudolph Hart

Hi bill.Just mix it at the correct ratio of base and hardner then thin as required to spray it.

Rudolph Hart

Forgot to add make sure you use an epoxy thinner.Normally you won't thin it more than 5 or 10%

In the aluminium boat building world i've had the opportunity to grind some etch off a recently sprayed boat.It completely penetrates the surface and will leave a stain behind that cannot be removed.

FILE IFR

Was that military aircraft?

496xl

No,I used it on general avaition and civilian aircraft.

jetmech05

I was using it on military aircraft in the mid 70's and probably later...I know my military aircraft had green in them... my last squadron was 84

FILE IFR

I see. I was under the impression they phased it out in the 1950's. Cool, now I know. Thanks.