North Australian FISH FINDER TM forums

This forum needs a "like" button.

Cheers for all the input lads. Il leave it as is. Has anyone put extra anodes on there actual hull? It's just disheartening to see your pride and joy start looking shaby because of bubbling paint......

My next boat will be fibreglass.....

Don't get despondent Barnzy.

The idea of another anode isn't silly but the one you've got should be enough providing its not corroded away and is still in good electrical contact with the motor body and that the motor body is in good electrical contact with the hull.

If you sleeved the motor anchor points there'd be no electrical contact with the hull which would then not have any anode protection and be susceptible to increased galvanic corrosion. The motor itself would still be protected ok but not the hull.

Just remember that electrolysis can sill happen and needs different attention but in this case we're talking about galvanic corrosion.

Take the little cavitation plate off and clean both surfaces so that there's good electrical contact to the motor body. Maybe a little conductive grease like graphite grease to help the electrical connection when you put it back. But only lightly.

But if you want to only look at the problems that you've encountered with your new console, look for corrosion points on the aluminium (white powder oxide) around any screws that you've used especially any stainless steel ones. I'd replace them with aluminium screws reducing any galvanic incompatibility and THAT is the most important thing you can do straight up.

This sort of stuff causes a lot of confusion in boating circles. Rusting, electrolysis and galvanic corrosion are 3 separate things and need to be addressed with differing remedies. Sometimes these things overlap like galvanising on trailers which gets rust, uses barrier protection initially then galvanic sacrifice to extend the protection. The trailer is like a great big sacrificial anode.

People who have these new alloy I beam trailers need to be particularly careful about fittings.

Happy to put up a bit of informative stuff that I've used to entertain fellas in the local tagging club about that sort of stuff if people want but a bit reluctant as I don't want to bore anybody.

Cheers ronjie. I might start tinkering around with the bolts ect.

Barnzy try duralac, its meant to stop the reaction between two dissimilar metals. I use it with good results especially on painted hulls.

Tefgel is another good protectant as well as duralac as scottie said when using disimular metal screws ect. It creates a barrier and stops the corrosion fairly well.

Duralac or mastinox as we know it in the aircraft engineering game is great stuff and cancerous.

Barnzy i have an anode on the hull and its as new as the day i bought the boat.

However the 5 little guys on the motor were half gone when I did the annual service last year. I will take a look at a couple of them later on to see how much they have gone in 10 months.

conductive grease like graphite grease to help the electrical connection

Barnzy

Been thinking a bit about the graphite grease.

Although graphite grease is a good electrically conductive material, the graphite itself in the grease has some galvanic properties which may complicate issues so probably best to forget it.

Yamaha causing "earthing" is bonding (for anode protection as mentioned) not earthing but the Sonic hub is a problem because all electrical equipment should be earthed back to battery negative not the hull because earthing to the hull (like a common earth in cars) will create slightly different potential differences ie. Voltages (pd = voltage) these voltage differences will cause electrolytic corrosion on the other hand positive voltage leakage will feasibly create cathodic protection but unfortunately ruin your battery. The bottom of your hull will be nice and shiny though. Best advice is if you need to use stainless fittings use Duralac or similar but better yet use monel rivets and try and plan fit outs to use a minimum of stainless steel. Personally I isolate the battery at both the positve and negative when not in use also.
Cheers,
John.

Gday John

Monel metal sits on the galvanic table close to 316 stainless steel Although corrosion resistance by monel metal itself is higher than 316, it has very similar galavanic characteristics and needs to be treated the same way on a metal hull. Physical isolation (no direct monel - aluminium contact) by spacers or Duralac.

I reckon that the shiny bottom effect is real electrolysis (as you say) and the problems associated with using "earthing to the hull" should have been recognised by manufacturers of maritime electronic equipment by now so that the negative power return from the printed circuit boards cannot be "earthed" to the hull no matter how hard somebody tries (dc isolator like a capacitor or a throbatron. Not a flux capacitor though).

Apologies, I was under the impression "Monel" was a trade name for sealed Aluminium rivets.

No mate.

Monel is an alloy of copper and nickel.

It has a very high corrosion resistance like stainless steel and is ideal in stand alone applications like on a f/glass or timber vessel.

Put it in direct contact with aluminium and you have a potential corrosion conflict due to the positioning of them on the galvanic table relative to each other. Monel is one of the "noble" alloys and aluminium is one of the "active" metals.

The name Monel is indeed a trademark name but the material isn't aluminium.

Wouldn't mind some advice from you about reels John. Maybe pm you?