Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Keats]

That is one big A$$ boat.

That prop looks like it is 6 foot in diameter....

[Hoist!]

Zincs, AKA Cathodic Protection.

The idea is to put a sacrificial annode in to take the electrolytic attack before it gets to the expensive chit!!!
Hoist!

[Keats]

The idea is to put a sacrificial annode in to take the electrolytic attack before it gets to the expensive chit!!!


Like pawns in a chess game.....

like infantry in a war


oh , forget it..............nevermind

Don's voices are getting to me

[porthole]

BB just a note - zincs are not for fresh water. The anodes are either magnesium  or aluminium. And they have to be matched to the boat, too much is just as bad as not enough.

[porthole]

.Zincs- never leave home without them.  Zincs are not cheap but they are cheaper than the alternative!!! 20 pounds each and the prop nuts are about 80. I usually put on about 2000 pounds. Next I suppose the  EPA will ban them for polluting, like they did copper bottom paint.

Tim,

The damage to my boat was in less then a week.

Interesting props you have there. Haven't seen anything like those on the boats around here. But then again most our fish boats are under 100' and use Kort's (the metal hulls at least)

[porthole]

Zincs, AKA Cathodic Protection.

"Cathodic Protection" can get a little more involved then just adding zincs 

[Hoist!]

"Cathodic Protection" can get a little more involved then just adding zincs 

Yep, we use a Cathodic Protection system to protect Titanium tubes in the condensers in refrigeration machines using river water as cooloing water. These annodes are connected to a monitoring system. The concept is to protect the equipment while sacrificing cheaper materials that attract the electrolysi,s before it attacks the expensive stuff!

From Wikipedia:

Cathodic protection (CP)
is a technique to control the corrosion of a metal surface by making it work as a cathode of an electrochemical cell. This is achieved by placing in contact with the metal to be protected another more easily corroded metal to act as the anode of the electrochemical cell. Cathodic protection systems are most commonly used to protect steel, water or fuel pipelines and storage tanks, steel pier piles, ships, offshore oil platforms and onshore oil well casings.

Cathodic protection can be, in some cases, an effective method of preventing stress corrosion cracking.

Galvanic CP
Today, galvanic or sacrificial anodes are made in various shapes using alloys of zinc, magnesium and aluminium. The electrochemical potential, current capacity, and consumption rate of these alloys are superior for CP than iron.

Galvanic anodes are designed and selected to have a more "active" voltage (technically a more negative electrochemical potential) than the metal of the structure (typically steel). For effective CP, the potential of the steel surface is polarized (pushed) more negative until the surface has a uniform potential. At that stage, the driving force for the corrosion reaction is halted. The galvanic anode continues to corrode, consuming the anode material until eventually it must be replaced. The polarization is caused by the current flow from the anode to the cathode. The driving force for the CP current flow is the difference in electrochemical potential between the anode and the cathode.

Potential problems
A side effect of improperly performed cathodic protection may be production of hydrogen ions, leading to its absorption in the protected metal and subsequent hydrogen embrittlement of welds and materials with high hardness. Under normal conditions, the ionic hydrogen will combine at the metal surface to create hydrogen gas, which cannot penetrate the metal. Hydrogen ions, however, are small enough to pass through the crystalline steel structure, and can in some cases lead to hydrogen embrittlement.

Hoist!

[porthole]

Gee Howie   you left off ICCP 

[Hoist!]

Gee Howie   you left off ICCP 

If ya need it Duane!

Impressed current CP
For larger structures, galvanic anodes cannot economically deliver enough current to provide complete protection. Impressed current cathodic protection (ICCP) systems use anodes connected to a DC power source (a cathodic protection rectifier). Anodes for ICCP systems are tubular and solid rod shapes or continuous ribbons of various specialized materials. These include high silicon cast iron, graphite, mixed metal oxide, platinum and niobium coated wire and others.

 
A cathodic protection rectifier connected to a pipeline.A typical ICCP system for a pipeline would include an AC powered rectifier with a maximum rated DC output of between 10 and 50 amperes and 50 volts. The positive DC output terminal is connected via cables to the array of anodes buried in the ground (the anode groundbed). For many applications the anodes are installed in a 60 m (200 foot) deep, 25 cm (10-inch) diameter vertical hole and backfilled with conductive coke (a material that improves the performance and life of the anodes). A cable rated for the expected current output connects the negative terminal of the rectifier to the pipeline. The operating output of the rectifier is adjusted to the optimum level after conducting various tests including measurements of electrochemical potential.

Hoist!

[icybay]

Duane,  They are  Nautican, 88-in-dia X 65-in pitch propellers on 8-in-dia stainless steel tail shafts. They are called "skewed" propellers and they are quite efficient and very common here. Designed in Vancouver BC and built, where else, in China.  Mostly I have nozzles on the boats.

I feel your pain, seen plenty of electrolysis. There is nothing that can eat a boat up faster than a bad ground or direct short in yours or the next guys Shorepower set up. You are lucky it didn't eat your block up. We even flush the toilets with fresh water to keep the corrosion out of the domestic systems.   Fortunately, my moorage in Seattle (Lake Union)  is in fresh water, thanks to the Ballard Locks, so it isn't much of a problem.

http://www.nautican.com/

[porthole]

They are  Nautican, 88-in-dia X 65-in pitch propellers on 8-in-dia stainless steel tail shafts. They are called "skewed" propellers and they are quite efficient and very common here. Designed in Vancouver BC and built, where else, in China.  Mostly I have nozzles on the boats.

Must be the difference between set and haul and draggers.

Most of our commercial boats are clam - scallop and net boats, so I guess the difference is the low speed high torque ops.

[SPIDERMAN]

BB just a note - zincs are not for fresh water. The anodes are either magnesium  or aluminium. And they have to be matched to the boat, too much is just as bad as not enough.

Actually not necessarily true. The trim tab on most pleasureboat outdrives is zinc whether the boat is used in fresh water or salt. As all of the other posts on this thread note, things get a bit more complicated where commercial or military watercraft is concerned. The Arleigh Burke Class Destroyers I've spent the last 20 plus years of my life working on, first as a designer, then an engineering liason and finally as Sr Homeport Rep responsible for the care and continuous maintenance of 12 of them in San Diego have a variety of anti-corrosion systems, both passive (corrosion resistant metals, zinc annodes) and active Cathodic protection. As such I am well aware of what's what when it comes to corrosion resistance.
As regards the boat I started this BATTERY thread on, it has fittings for anodes on the stern if the boat is used in salt water. One of the many little details that have made this purchase the find of a decade.

B B

[SPIDERMAN]

Inverter?

Inverter takes 12volts DC and outputs 110 AC. The higher end models double as a charger. That sounds unlikely with the size of the boat you have.
If it is a "converter", 110 AC down to 12 DC that does not belong on a boat!

I did say it wasn't right in my post didn't I ? Yup, I did. There were a some 110AC "things" on the boat that the previous owner stripped off when I bought it. For whatever reason, he left the inverter. The way he had it set up was with alligator clips that he connected when using the "things" in question. Since posting about it, I have told my buddy to yank it as I have no use for it. If I put a stereo in the boat it will be compatible with the boats electrical system.

On another note, this boat will sit by itself in a secluded cove of a fresh water lake. The closest boat to it will likely be 1/2 mile away at the far end of the cove since there is only one other remaining property owner in this cove. The cove is at the extreme end of a no body contact area and the Public Water District that controls the water supply has bought out all but 6 property owners with in the 2 mile non contact zone. Hence on another thread somewhere I mentioned installing a 15,000 gallon swimming pool on the property this summer. But I digress. I am no dummy, just a few years since my last small pleasure boat and far far over the line into extreme duty Naval applications. That's why I started this thread. I was hoping for a KISS not rocket science. I've been paid handsomely for years for rocket science. I need to dumb down and be a weekend Gilligan again.

B B

[hogasm]

Big B...install a boat lift and tell us to KYA

really if you do install a battery charger...which you should if you keep the boat in the water.....get a marine grade one.
the first post Duane posted with a charger and bulkhead connector from Boat US or West marine is all you need for your boat.

[hogasm]

This is a picture of one of the shafts.

Most of the damage was on one side, the side closest to the other boat, but you have to change this stuff in pairs.

Props $3200
Shafts $2100
Rudders and related install parts $1800

And a boat load of miscellaneous stuff to go with it.

Nice work by your neighbor....One problem with keeping ones boat in the water is that you are at the mercy of your dock buddies as to how they maintain their equipment. The guy next to ours last year was as tight as they come on maintenance. Needless to say it only took a few talks with the dock master and the DM to talk to him before he left.

Haulouts were alot cheaper after he left