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galvanic corrosion

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jasoncalleja

Regular Contributor
hi i would like to know what can i do for galvanic corrosion it is causing engine water passages built up blockage and this is new 2 year old hydraulick steering cylinder shaft cheeping because of galvanic corrosion i never leave the boat in sea and always washed and garaged after each use what can i do to stop it
 
I assume that you are talking about your Honda.

On the very bottom of your stern bracket there should be a large rectangular anode. Check that it is there. Remove it. Sand down the facing on the stern bracket until it is bare metal. Sand down the opposite face on the anode and reinstall. If anode is highly corroded, replace it. I believe on your engine, the part number should be 06411-ZW1-020. But check on boats.net for your specific engine.

There should also be a grounding cable from one of the anode bolts to the stern bracket. Make sure both ends of that cable are making good contact and there should be no resistance from one end of the cable to the other.

You probably should do the same for each of the two smaller anodes on each side of your lower unit.
 
If you don't leave the boat in the water, you are highly unlikely to be experiencing galvanic corrosion......
 
I need to disagree with Makomark a bit on this. I keep my boat on a lift. Maybe four ot five times a year it sits in the water at a private pier overnight when I can't get it on the lift. But I still get corrosion. Anodes get highly pitted and need to be changed out about every three years. Each year, I must grind down the surfaces because they get corroded and pitted so badly from year to year.

There is one other issue. If you park in a marina where they have electrical outlets to at least some of the slips, there may be some bad grounds that turn the marina water into one big battery and can feed a very rapid corrosive process. Boat US has several articles about that on their website.
 
yes makomark i dont leave the boat in sea. and yes CHawk 25 the anodes are there and my problem is that they are like new as i use the boat for around 20hrs every summer which i think it means that the steering stainless steel shaft had absorbed the galvanic corrosion and i whish to eliminate the problem as the steering cylinder cost a bit more than anodes lol. are there any other type of anodes that are designed for my situation?
 
OK. First, is the little cable in place connecting the big anode to the stern bracket? Are the facings between the anode and the stern bracket clean and have good metal to metal contact?

If all of that, I'm guessing that your steering cylinder my be sufficiently isolated from the engine brackets to not get the sacrificial benefit of the anodes.

I imagine that you can attach an external anode to the cylinder itself using very shallow bolts. You can purchase all kinds of anodes on line, in all kinds of shapes and sizes.

I was once told to never mix anode materials. However, on the Honda engines, the external anodes are zinc, and the internal ones in the manifolds are some sort of aluminum composite. Magnesium anodes should only be used in fresh water.

BTW - is your boat fiberglass?
 
if there isn't any electrolyte, there can't be galvanic corrosion.....the point is until you know what the cause is, you can't treat it effectively....in other words, anodes used to treat mitigate galvanic corrosion won't help much in a non-galvanic situation.

if there's a 'higher learning facility' close by, you may want to swing by and see if there's somebody with a good (broad) chemistry background....another option would be taking several good pics of the cylinder and call their tech support line....
 
My boat is a R.I.B (rigid inflatable boat) yes the small cable is there attached to the big anode that is attached with the stern bracket. what i cant under stand is that the steering cylinder is attached with the stern bracket so this means that it is in contact with the stern bracket so it means that the big anode is absorbing electrolyte for the cylinder too. i have also a aluminium bracket that i thing it may absorbs some electrolyte too i will retry to remove the anodes and sand them with some abrasive sand paper. do the bf90d 2010 have internal anodes and if yes where are located?
 
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OK on removing and sanding faces of anode and the face of the bracket where it mounts.

As for internal anodes - yes. They are on the cylinder head. See item 1 at:
http://www.boats.net/parts/search/H...d Later/BF90DK2 XRTA/CYLINDER HEAD/parts.html

However, these are aluminum alloy anodes and last for a very long time, so I doubt that is your problem. I replaced mine at 1500 hours of all saltwater running, and they were still in pretty good shape.

As Makomark suggested, contact the manufacturer of your steering cylinder and see what they have to say.

You also might post pictures so that we can take a closer look at the problem.
 
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Well, the replacement steering cylinder sounds like a good deal. I couldn't see that much corrosion on that cylinder in the pictures.

Is it leaking at all?
 
no it is not leaking for now but i think it will do shortly. now i have found this on there annual maintenance schedule

Ram Inspection - Lastly, inspect the steering tube and support rod, take a look at the exposed ramshaft and make sure everything moves smoothly as the engine pivots from side to side. Take a closelook at the seals and wipers, and check for any bends, nicks or damage to the steering ram shaft. (Ifyou boat in saltwater, make sure you’ve installed a grounding strap to protect from galvanic corrosion.)

to where shall i connect a grounding strep? to the same wire on the stern bracket to the big anode?
and if the cylinder is attached with the tilt tube why it is absorbing the electrolyte does this mean that the anode is not working?
 
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Ground strap should be connected to the stern bracket. Do they show you where to attach a ground strap on the steering cylinder?

The only reason an anode will not work is that it is not in good contact with the stern bracket or the engine mount itself.
 
I found a picture on Google it shows you where to attach to the cylinder ram but don't show where to attach with the motor. I thought i would conect it to the big anode direct. What do you think?
 
That would probably be the most convenient place. Just put an O connector on the end of the strap so that you can slide one of the two two bolts used to mount the anode through it.
 
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