Headliner screw/washer rust

[DesertNomad]

On my Piper Dakota, I am seeing a bit of surface rust on some of the washers on the screws that are in the plastic headliner piece (the part with the cabin light). There is no rust on the screws themselves, only the washers. Has anyone else seen this?

I guess I need to replace these. As far as I know there are no leaks in my cabin - at least I have never seen any.

The airplane is hangared in Nevada but spent a couple months in the Portland, OR area getting maintenance done (it was hangared there too). The only pictures I have of it are from 3 years ago and although blurry, they don't seem to show any rust.

 

[smv]

Pretty good chance the humidity in Portland is quite a bit higher than pretty much anywhere in Nevada...

Take 'em down, carefully brush 'em off with a soft bristle (like brass) brush. Put 'em back until the next time it comes back from Portland.

 

[DesertNomad]

Yeah - seems like 2 months wouldn't be enough for this but perhaps so. It's weird that only some of them are affected - even the 4 up front on top of the window divider post (which are all right next to each other) has only one of them affected.

 

[smv]

Yeah - seems like 2 months wouldn't be enough for this but perhaps so. It's weird that only some of them are affected - even the 4 up front on top of the window divider post (which are all right next to each other) has only one of them affected.

Hmmmm... Are they supposed to be stainless steel only to have some of them lost by the mechanic and replaced with whatever he could find on hand?

 

[DesertNomad]

Hmmmm... Are they supposed to be stainless steel only to have some of them lost by the mechanic and replaced with whatever he could find on hand?

Certainly possible, though I don't think any of them have been removed during the 5 years I have owned the plane.

 

[Bell206]

Has anyone else seen this?

Yes. Depends on what the washer base material and/or plating is whether they corrode. But it's not just humidity that causes corrosion. Some cleaning chemicals can cause it also and the quality of the washer also play into it. Aircraft Spruce, etc have them.

 

[Plano Pilot]

Hmmmm... Are they supposed to be stainless steel only to have some of them lost by the mechanic and replaced with whatever he could find on hand?

I agree. Take the worst one out and see if it sticks to a magnet, it should not or weakly. Quality SS washers are not that expensive, I would replace them with quality ones.

From West Marine.

"What is the best grade of stainless steel?
There are three types of stainless steel commonly used for fasteners: 18-8, 304 and 316. The easiest way to look at it is to remember: the higher the type number the higher the corrosion resistance. Meaning, 18-8 stainless steel is less corrosion resistant than 304 and 316 stainless steel offers more corrosion resistance than 304.

While boaters often focus on the corrosion resistance properties, there is a cost to this extra protection: strength. Because of the alloy composition, there are differences in the tensile strengths of each type of stainless steel. To simplify it: the more corrosion resistant the fastener, the lower tensile strength. In many cases this difference is minor and opting for the more corrosion resistant material will not affect the holding power. In other cases, the choice of a weaker material can make a difference."

I would do not think you need to worry about strength for this application. Look around the outside edges of the plastic headliner for signs of leaks.

 

[DesertNomad]

Yes. Depends on what the washer base material and/or plating is whether they corrode. But it's not just humidity that causes corrosion. Some cleaning chemicals can cause it also and the quality of the washer also play into it. Aircraft Spruce, etc have them.

I can't imagine cleaning chemicals were used there. More likely the humidity while it was up in Oregon... though I have taken it to Florida and all the way up to Maine on various trips. Always hangared. I don't see any evidence of a leak - no discoloration anywhere on the headliner.

There is also the chance that it has been this way for a while and I just noticed it.

 

[Bell206]

I can't imagine cleaning chemicals were used there.

I guess "cleaning chemicals" was the wrong word to use. Some very benign liquids like soap or tap water in some cases can cause a localized reaction and lead to the rust/oxidation of the washer. At the old day job we went to nylon trim washers as we were changing the washers a lot.

 

[Dan Thomas]

Condensation of the moisture the occupants breathe out is one of the major sources of water in the ceiling. In flight that ceiling gets cold, and water condenses on anything cold enough, especially metal. Removing a headliner often exposes plenty of corrosion of the interior of the roof skins. The Cessna 177 and 210 can suffer dangerous spar carrythough corrosion, too. Same source.

Radio problems, including alternators that go offline when the mike is keyed, are sometimes due to corrosion of the antenna bayonet connection in the ceiling. The grounding of the cable shield is lost and RF escapes to cause issues with ACUs and ELTs and other stuff, besides Com problems.

 

[DesertNomad]

Condensation of the moisture the occupants breathe out is one of the major sources of water in the ceiling. In flight that ceiling gets cold, and water condenses on anything cold enough, especially metal. Removing a headliner often exposes plenty of corrosion of the interior of the roof skins.

They did put a new antenna on top when I upgraded from the 530W to the 750 3 years ago, but I don't know if they used the existing antenna cable. Either way I guess they would have had to take the headliner out. The plane is very clean in general (SB1006 was done last year and very clean indeed). Just don't like to see rusty screws anywhere.