Will Zinc React Unfavorably with Aluminum

From: metaloffcuts.co.uk/shop/sheet-metal/​sheet-metal-zinc.html

Zinc is compatible with aluminium and stainless steel and can be included in building features. Zinc sheet metal is traditionally used to create distinctive long lasting architectural building features and finials.
Zinc is also used in interior design to create rustic charm and character in features such as countertops, tabletops and splashbacks.

Good luck. It looks quaint.

..........OK so far, only from an electrochemistry perspective the zinc is more electropositive than the aluminium, therefore the aluminium will corrode preferentially over time. So they need to be electrically isolated from each other when used in the same structure for the best results. Otherwise there will be tears....(this type: ).....

No worries. Zinc strips to control the moss will be fine. Most houses use aluminum gutters and in my case this hasn't affected them for over 30 years.

Lyn/PW/Pete,

Thanks for the replies.

I am thinking I will butt the zinc up under the aluminum ridge vent, as far as isolation between the two, just to be safe, I can isolate with roof felt double folded.

I am only tucking under about an inch so no major inconvenience with that.

_{Now that we have that resolved, can I interest one or all of you to come over and install this? As I have gotten older, heights and falls have become less and less appealing to me}

Rorschach,

Thanks for the tips. I will definitely look into the copper oxide granule shingles and the plastic ridge vents when replacement time comes!

Thanks again - KJK

If you were to have a ridge vent bent up out of copper sheet instead of aluminum (or plastic) you'd probably NEVER have any lichen ever again.... but it wouldn't be cheap.

Paint the aluminium with copper sulphate solution. This will cause the copper to replace some aluminium, and give it a coppery sheen. With any luck, the copper will leach down on to the roof and do its work. Obviously you need to redo the application from time to time. Just suddenly occurred to me, thinking about the miners throwing aluminium cans into a copper tailings dam, and making a few bob on the side selling the resultant copper.

I have had good results using the Zinc strips at the peak of the roof.

I have also had good success with an annual "Moss be Gone" treatment on the trouble spots. I just tried to find the stuff I used to use, but it looks like it might not be available anymore.. It was a white granule powder that was applied dry, and rain would dissolve it and run it into the moss and kill it.

A ol' fashion push broom does a decent job as well.

RVZ/Pete,

I have used the powders, the liquids, the home remedies. They all do a great job but the lichen returns within a couple of weeks.

I will look up "Moss Out" though. I had not found this one during my research.

I have lived in this home since 2004 and had no problem until fall of 2009.

Roof was 4 years old when I moved in.

I have a row of assorted pines to the north and then swinging around to the west for wind block.

When the lichen originally started to grow I thought it was sap from the pines. The following spring I realized it was lichen.

I'm going to try the zinc (already bought it) and see what happens.

Thanks again for your input - KJK

Have you tried repeated dosings of a good Algaecide sold for swimming pools?

Milo

Hi Milo,

No have not tried that.

Are you thinking something like Shock?

no shock is a strong Chlorinator, he means a liquid algaecide to prevent algae growth. something like this.

Lichen is a symbiosis between a fungus and an algae. Pool chemical companies make specific algaecides I will send you a picture of the one I have at home tomorrow.,here's one off the web.

Shock and sanitizer are different. Algaecide is designed to kill algae.

Milo

Consan may work as well....

Milo/Rorschach,

Thanks for the product references, I will look into these.

Regards - KJK

Hi John,

Yes, unfortunately lichen does cause damage.

As it grows it lifts the granules from the substrate leaving dark marks (substrate) behind.

From my research, lichen is not good for asphalt shingles, at least not good for cheaper shingles as I apparently have.

Regards - KJK

Zinc in contact with aluminum is not a problem. In fact, aluminum is frequently coated with zinc prior to applying other finishes. They are close enough in the electromotive series that you won't have a corrosion problem.

welderman,

Thanks for the heads up. This was a concern for me, I did not want to eliminate one problem and create another.

Thanks again - KJK

The zinc needs to be exposed to the rain and weather so that the formed zinc compounds wash down over the roof. It is the zinc compounds that kill the moss. With typical acid rain it forms, I believe, zinc sulphate salts. Perhaps someone can confirm the chemistry.

Concur on this note, the zinc must be exposed to the rain to wash zinc molecules down the roof to keep the algae spores from blooming.

A strip of lead would work as well. If you have any plumbing vent pipes with lead boots or galvanized covers around them you will probably notice that nothing grows below them on the roof.

It is the leaching of the heavy metals by the rain running down the roof that keeps it clean.

129CBRider,

Very good point!

I did notice no growth around the vent pipes.

My vents are zinc clad which is what got me looking into the zinc strips.

Thanks - KJK

Hi GW,

That is pretty much what I had assumed based on my research.

A neighbor of mine has zinc trips on the roof of his milk house that were installed about 15 years ago when he replaced the roof. The old boy swears by the stuff.

Thanks - KJK

Here they apply a copper strip using double sided tape. Appears to work....

Hi Andy,

I had also read about copper but was concerned about the green patna (sp?) appearing and staining the shingles.

As Rorschach pointed out, there are also premium shingles available with copper oxide granules which I will look into when it is time to re-shingle.

Thanks for stopping in - Regards - KJK