Metallurgy 101

[chillihilli]

Hi all,

I'm doing some mods to the Swing, one of which is a permanent mount for my bargain triple swivel mount rod holder. I've got some good ideas on how to make a nice solid mount without drilling any new holes - one of which involves the use of Aluminum bar/strap about 2 or 3mm thick and about 50mm wide. I haven't used aluminum in a kayak application before so my questions are:
- Does aluminum rust after contact with salt water (I assume not give the vast number of "tinnies" out there on the water
- Will I get any metal to metal reaction if I use stainless steel screws in it?

Again I assume not, but want to make sure. Thanks in advance. Pete.

[maverick]

Ally is fine in salt water, just wash it down like everything else. You should try to avoid mixing metals - Ally + Stainless + Saltwater can be a bad mix. If you need to pop rivet ally or other metals together trying using monel pop rivets, they are inert (I think is the corrrect teminology but I am happy to be corrected).

And a liberal dose of INOX after washing, for gods sake don't use WD40 or RP7 otherwise you will be shouted at on the forum .

[bilby]

You will be fine using stainless screws, you will get a little corrosion from the two dissimilar metals but if you wash it and use INOX you will be right. You can buy a product called Duralec which creates a barrier between the two metals, but its pretty expensive at $30 a tube but is a great product.
Cheers Bilby.

[2rsea]

There are many grades of ally which can be anywhere from very good in saltwater to an aspirin. Most of the material you get in flatbar though is fine make sure you give it a wash with fresh though. Stainless & ally do not agree with each other as a rule but as has been mentioned washing & inoxing reduces this considerably - the absence of any electrical current travelling thru also helps. As bilby said duralac is designed for exactly this purpose, loctite 222 & 243 will also help & are a bit cheaper if you were going to bother but on a yak I reckon the wash n' inox method is all that is required. Cheers Nick.

[Tormentor]

When alimunium corrodes it forms the oxide which forms platelets and this "skin" protects the metal underneath dissimilar metals in contact will cause more corrosion especially in water containing electrolytes (salt).

To minimise this you could try to use fibre washers or a dab of varnish under the screw/bolt head or coat the head afterwards or get the whole lot plastic coated/powder coated to match the yak .

I wouldn't be surprised if you can't get ally rivets so that would also work