Best screw material to use on Exterior aluminum?

[Beatty1950]

Sent: 8/12/2004

I assume the exterior of my 1975 Winnebago Brave is Aluminum.   Correct ?

If correct, I heard today that stainless steel and aluminum don't mix well.  I am in the process of replacing my exterior screws with new longer stainless steel square head screws.

Is this a bad idea?   If not stainless steel screws then what type of screws should I use?  I prefer to not use aluminum screws since they appear to be not very strong.

Thanks for the advice.

Dave Beatty

[chip]

Sent: 8/12/2004

galvanized hardware is your next best choice. i used mc feeley's no corrode square drive fasteners when i put my rig back together. i have seen no noticeable action between the panels an d the screws for almost fours years and i live very close to the ocean.
i also NEVER broke or, cammed out a single screw and used a lot of pt wood to reassemble.

[Sea Hag]

Sent: 8/14/2004

Yes the panels are aluminum. stainless steel should be ok with the aluminum but a little pricey. regular steel or galvanized react with aluminum. I.m not sure about zinc coated screws but they would be my next logical choice. You also must be aware of what the screw is going into underneath. On the grill for example you are going through aluminum then into steel . If you used aluminum screws it would react with the sheet metal. I used stainless recently on my grill section. Sea Hag

[lockman]

Sent: 8/28/2004

The PO had replaced all the screws along the top corner caps and end caps with longer stainless steel screws. I think he was trying to overcome the rotted wood underneath. They caused no reaction problems we could tell and we reused them after redoing the roof. Beware of longer screws though!!. He had punctured a live wire to the clearance lights causing a nasty short. It looks like it caused him as much grief as it did me although I did eventually find it. On the other hand a large number of trim and window screws were replaced with plated. They have rusted quite badly and stained the paint. I am in the process of removing cleaning and replacing the worst of them. Budget says (free) to use plated at this time and stainless when I find a cheaper source.   

[Oz]

Sent: 2/10/2006

I had removed a lot of rusty replacement screws on the body trim I spent days sanding and polishing last year.  I replaced them with stainless.  They were pricey compared to anodized, but not too bad as I bought a whole pile of them from a mom and pop hardware store and they gave me a break.  They've been through all kinds of weather and there doesn't appear to be any chemical reactions with the aluminum so far.  They still look bright and shiny.  As they should... for the price.

- Sob

[SPEC_OPS121]

Sent: 1/17/2007

I had to replace the awning rail on mine years back and after each screw was removed i shot a small amount of Gorilla Glue into each hole.
I also ran a bead of silicone along the upper back side before it was pulled up against the trailer.
Not a single screw has loosened nor have there been any leaks.
I'm not certain I'd ever get the screws out since i used Gorilla Glue but i have no intentions of ever having to remove it.
Gorilla Glue is quite good.
stephen

[tiinytina]

Sent: 2/12/2007

speaking of this.... Just wondering.... every frickin' screw on Gone is a square head... which I find obnoxious as many of the external ones are rusted out. We have been replacing them with stainless philips heads. Gone is exterior aluminum.

Am I doing a bad thing?
Tina

[tatkin]

Sent: 2/14/2007

I have to ask ?  If  I use any old screw and then cover it with a silicon sealant ! am I still looking at future ? deterioration. ...

[tatkin]

Sent: 2/14/2007

Never mind , I see the awning fix response now ...   

[moparmotivator]

Sent: 2/16/2007

We manufacture enclosed trailers and truck bodies with aluminum skins and steel frames.

The steel is painted as well as the skin so there is little to no reaction between materials for a long, long time.

We use the double square drive, zinc coated, button head self drilling screws with good success.  The button head is big enough to keep from ripping through, and as an added bonus it covers up the scarred paint from the drill chuck bottoming out.

The square drive beats the heck out of phillips if you are doing a lot of them.
A lot cheaper than stainless also.

[JCMAC]

Sent: 2/18/2007

  Having spent many years in the ocean engineering environment, I would recommended several choices of fastener - compatible with aluminum.
1. The best would be cadmium plated stainless steel, but this is expensive.
2. Cadmium plated steel is OK with aluminum, but will eventually rust - depending how far you are from the ocean.
3. Stainless steel, as mentioned is good as small amounts of stainless is compatible with large amounts of aluminum, from a galvanic corrosion view.
4. Aluminum screws are not very strong, but this is what they used on the corner (radisused) molding on my '73 Chieftain.
5. I would not use galvanized hardware.

mac