Brass vs bronz screws?

[Benz]

Originally Posted by skipmac

Stainless into aluminum is a huge problem unless you use Tefgel, Lanocote, Loctite or some other kind of goop to electrically insulate the SS from the Al. If you don't, a couple of years down the road the SS fasteners will be permanently and irretrievably frozen into the Al by the galvanic interaction between the two metals.
,

Over my years of boat ownership I have had to drill out, grind out, cut out and otherwise mangle Al things like masts, hatch frames and such to get out the SS fasteners that had welded themselves into place. I have tried every kind of penetrating, freeing, loosening chemical and technique known to man included soak and heat, soak and beat, soak and heat and beat and repeat. Have used superheating and still end up drilling out the majority of the SS fasteners.

Bedding, for 99% of the bedding I use butyl tape. The stuff is fantastic and you can get it off again if you need to without using HE.

It was a mistake on my part to assume that some sort of goop (tef-gel is my favorite) was a given. My apologies: no matter what metals you put together, ALWAYS use an anti-seize. That said, stainless into aluminum is far better than bronze into aluminum, and forget putting bronze and galvanized steel together--that's a recipe for disaster, anti-seize or not. But this thread is not about electrolysis, so suffice it that bronze is still my all-time favorite.
Ben
zartmancruising dot com

[skipmac]

Originally Posted by Benz

It was a mistake on my part to assume that some sort of goop (tef-gel is my favorite) was a given. My apologies: no matter what metals you put together, ALWAYS use an anti-seize. That said, stainless into aluminum is far better than bronze into aluminum, and forget putting bronze and galvanized steel together--that's a recipe for disaster, anti-seize or not. But this thread is not about electrolysis, so suffice it that bronze is still my all-time favorite.
Ben
zartmancruising dot com

Guess you can tell from the vehemence of my reply that I HATE stainless in Al, at least as it seems to be most commonly done IE without any goop of any kind. I hate to count the number of hours I've spent getting SS screws and bolts out of Al. So based on my experience with a number of boats I just didn't make the assumption that that the use of anti-seize as a given. Apparently you've been there, done that.

I do like bronze, especially underwater or any wet environment. Still have the original bronze prop shaft on my boat and hope I can keep it, but I think SS would be stronger. Yes an issue with crevice corrosion but well bedded to keep the hole dry should be fine.

And yes, any copper based alloy with Al is a big nono, even with a good coating of Tefgel or whatever.

[Benz]

Originally Posted by skipmac

Guess you can tell from the vehemence of my reply that I HATE stainless in Al, at least as it seems to be most commonly done IE without any goop of any kind. I hate to count the number of hours I've spent getting SS screws and bolts out of Al. So based on my experience with a number of boats I just didn't make the assumption that that the use of anti-seize as a given. Apparently you've been there, done that.

I do like bronze, especially underwater or any wet environment. Still have the original bronze prop shaft on my boat and hope I can keep it, but I think SS would be stronger. Yes an issue with crevice corrosion but well bedded to keep the hole dry should be fine.

And yes, any copper based alloy with Al is a big nono, even with a good coating of Tefgel or whatever.

I've wished for a long time now that aluminum fasteners were more readily available. I'm sure if sized correctly they would be just the thing. When building my mast, I used the minimum of SS fasteners I could, and would gladly switch them all to Alu if I could feel confident in the engineering. In the meantime, I buy Tef-gel and Lanocote by the half pint, and urge my friends to do so as well.

[GordMay]

Originally Posted by Benz

I've wished for a long time now that aluminum fasteners were more readily available...

➥ ALUMINUM FASTENERS SUPPLY COMPANY

➥ Fastener Express - Socket Head Cap Screws, Metric Screws , Fasteners and Anodize - Aluminum Screws, Fasteners Nuts Washers

➥ https://www.fastenal.com/products?te...steners%22%7C~

[Benz]

Originally Posted by GordMay

➥ ALUMINUM FASTENERS SUPPLY COMPANY

➥ Fastener Express - Socket Head Cap Screws, Metric Screws , Fasteners and Anodize - Aluminum Screws, Fasteners Nuts Washers

➥ https://www.fastenal.com/products?te...steners%22%7C~

Thanks Gord--that's a goldmine!
Ben

[30West]

Originally Posted by skipmac

Stainless into aluminum is a huge problem unless you use Tefgel, Lanocote, Loctite or some other kind of goop to electrically insulate the SS from the Al. If you don't, a couple of years down the road the SS fasteners will be permanently and irretrievably frozen into the Al by the galvanic interaction between the two metals.

Agree on using thread locking compound, not to insulate as they will touch, but to keep out moisture. Thread locking compounds turn to a plastic that seals out moisture: no moisture no corrosion. I use low-strength thread locker anywhere I don't use medium or high strength to hold the fastener secure. Anti-seize is not as good, tends to rinse out over time, or dry out and wick in moisture. Unsealed threads tend to wick in moisture by capillary action.

Stainless and aluminum are far apart on the galvanic index, they will set up basically a small battery and corrode in the presence of moisture, especially salty moisture.