steel and aluminium????????

[choppa]

is there anything wrong with bolting steel to aluminium,,,,

other than the obvious,,,,,,,,,,,, rust

my good old next door neighbour and friend for a few more days,, has welded together a ""roll bar"" for the the tinny,,, dunno why,, he just did,, and he wants to know if i want a few holders etc etc,,

not that i can't weld my own i say,,, but he's nearly 70,,, loves fish'n,, and its probably his way of securing a seat on the next voyage,,, but somewhere in the back of the brain,,, i'm hearing alarm bells

choppa

[Hamish73]

I cant see much of a problem, most engines have alloy heads/blocks with steel components bolted to them.

[Owen]

It will rust, and it will corrode your tinny if you bolt the two faces directly together.
To have any chance you have to galvanise it and use the usual insulating tricks when bolting it on. i.e. No steel or stainless contact on the ally.

[grey_inflatable]

mate were you bolt it on try putting a bit rubber this should prtect your boat and reduce any vibration but im no expert but love to weld thinking of making a roof rack on my traier cheers

[finga]

Listen to those bells mate.
Even when it's been hot dipped it'll be troubles.
Zinc and steel are miles from ali on the activity series and corrosion of the alloy will happen pretty quickly.
Even with the gaskets salt water is going to get in and then an electrical circuit is made...corrosion is there to stay.
The chap that I got 'Junior' off had galv. eye bolts to hold the tinny on the roof of his 4X4. It was only 3 years old when I got it and two of the bolts were lucky not to have fallen out due to corrosion. The bolts were also sealed/insulated with sikaflex between the washers and hull
Another 'concern' would be the rigidity of the steel and how it's attached to the tinny. If the 'cage' is too rigid it'll fatigue the mountings on the boat if not mounted properly.
If it was me I'd be taking him fishing without the 'cage' and say how nice it is to have nothing in the way when fishing or that your gunna bung a bimini on and the 'cage' wouldn't be an option.

[Noelm]

in actual fact, galvanizing will make it worse, plain old Steel on Alloy is kind of OK, but it will rust and make a mess, Stainless and Alloy will react together and slowly stuff up the Alloy, Brass and Alloy is a definate NO the Aluminium will be "gone" before you know it

[saurian]

Choppa correct , alarm bells . Steel will cause corrosion of alloy , even stainless.
A product called duralac is available to "inhibit electrolytic corrosion between dissimilar metals". It is like yellow silicone , very messy and if you get it on marine carpet it is stuck for good. Just seems to smear within the piles.
I always put thin rubber pad between stainless and alloy , with duralac on any drilled holes and fixtures, ( bolts, screws, rivets etc.....)
Costs about $ 25 for 115 ml tube which will last ages/years.