Frugal HX pencil zinc mgmt. LOL!

[Noah]

Changed my HX pencil zinc today, after 8-mos.  Probably a little on the long side...ya think?! Looking really sharp!

[Craig Illman]

Check to make sure there wasn't a piece left in the HX too. They seem to wear out in the middle. I found a couple remainders in mine, left by the PO.

Craig

[Breakin Away]

Looks like you may have a stray current issue. Do you leave your boat plugged in? Do you have a galvanic isolator?

[Noah]

No stray current...and no isolator. Well mantained electrical system at YC docks. After 8 mos. in salt water HX on a 2-1/2 in long pencil zinc it looks about "right" to me. I just let my HX zinc go too long. The HX is only 1-1/2 yr. old and I usually change zinc every 4-6 mos.I also have 3 other zincs (Flexofold prop zinc, prop shaft and strut). All are checked monthly by my diver and changed when they get to about 50%. Each one lasts a little different timespan. Flexofold zinc is ready to be changed next month after protecting 13 mos. that's an investment I don't want to skimp on!

[Ron Hill]

Noah : The Zn life also depends on whether the Zn is 3/8" or 1/2" diameter, besides the brackishness of the water.
With my old engine I could get by for a season with a 1/2" Zn.  My new engine had a 3/8" diameter and needed to be changed in mid season. 

A thought

[Stu Jackson]

and mine only lasted 3-4 months in SF (never plugged in).

Recommendations have always been to get to know your boat and find out what the intervals are for YOUR boat where IT floats.   

[Noah]

Mine is 3/8 in. zinc and in my laziness, just waited a bit too long before swapping it out. Always the case with me when it comes to working on my iron jib. PS-- Ken, it has been 7-mos and I still haven't installed my "new" Oberdorfer. Bout ready to tackle it before I regret it and learn the hard way.

[KWKloeber]

No stray current...

Why do you say that?  Checked it or just surmising?  Are you saying on yours, or on any other boat in the marina?

Ken

[Noah]

Just a semi-educated guess as no obvious symptoms. My neighbors are "well maintained" boats and very a close knit group and none have reported problems.  There is a pretty savvy onsite maintenave crew at our YC and I am told they check each shore power box on a regular bases. Plus there is also 24 hr. onsite security who walk each dock several times a day and look for cords in the water and other out of place stuff. Still, I guess there could be stray current?? Would you recommend I check based upon one neglected pencil zinc and if so how would I check for it?

[KWKloeber]

noah,  well-maintained shore facilities actually have little to do with 12v stray DC current on the boats. 
In fact, well maintained (good, well-connected, low V loss grounds) make galvanic corrosion more prevalent because that's the precise path of the current from boat to boat.  I thought maybe you had a gavlv. isolator or had the 12 neg and AC ground unbonded -- that's they only way to be assured there is no potential for GC (well, along with keeping your shore cable disconnected of course.)  Of course in salt it's more prevalent than fresh due to the high conductivity.  A simple pc of equipment or a battery charger that otherwise looks fine can be leaking low V to the DC negative (or more likely could anyone elses be leaking and not know it!)

I know the galvanic potential can be checked -- I have never done it and unsure how to/how sensitive equipment needed, but mr google probably has an idea.  I will shout out to my boat electrician buddy also.  I brokered an aluminum Marinette 32 (alum hull) that had a corrosion potential meter built right into the helm panel.)

-ken

[Ron Hill]

All : Check your Zns frequently!!

Zinks are a lot cheaper $$$ than a new heat exchanger!! 

a thought

[Noah]

I agree Ron!
And thx Ken, but I am not worried and very confident in the integrity of my 12 volt charging systems and wiring--all is new and properly/professionally designed by an experieced electrical engineer and installed by a top marine electrician. The "wasted" pencil zinc issue is just me waiting a few month too long to change in salt water environment.

[KWKloeber]

NOAH!

I believe that I'm not clearly stating what causes galvanic corrosion.  It has NOTHING to do with YOUR boat or MY boat and how well WE are wired.  It's everyone else (not "every"one -- but potentially ANY SINGLE OTHER boat connected to shore power.)

Saying you have a well-designed/installed electrical system, I don't care if Thomas Edison designed it -- is tantamount to claiming, "I can't have had a collision because I just had my vehicle inspected."  And then a someone's brakes fails at a stop sign and T-bones you.

I'm NOT saying YOU have galvanic corrosion, or saying it's apocalypse waiting to happen, but anyone that has a bond between the AC and DC (and no galvanic isolation) HAS as much potential for GC as another poorly maintained/designed electrical system (in fact, it CAN be GREATER potential than on the boat w/ a poorly maintained electrical system.)

That's absolute fact, not blowing smoke!

-kk

P.S., zincs in a Hx do not "dissolve" -- they electrically corrode (as yours did.)  Think about this -- if they did corrode away, broken off pieces of zinc wouldn't be an issue re: blocking the cooling system!!  They would "dissolve."   
Hang a zinc over the side of your dick and check it a year later and see what happened

Let's step backward away from boats to "every day" -- zinc coating is used to PROTECT metal FROM salt water corrosion!!! (i.e., a galvanized bolt, right?)

I agree Ron!
And thx Ken, but I am not worried and very confident in the integrity of my 12 volt charging systems and wiring--all is new and properly/professionally designed by an experieced electrical engineer and installed by a top marine electrician. The "wasted" pencil zinc issue is just me waiting a few month too long to change in salt water environment.

[KWKloeber]

Anyone wanting to check.... below is the method (from my trusted, catalina owner, also experienced, electrical engineer.)

-kk

Disconnect the shore power cord at the boat's inlet.

Remove the bond wire (if present) between the AC ground (green) and the DC negatives (probably on the negative buss).
Also disconnect your shore charger from the batteries -- as it can also bond between the AC and DC (or unplug it if it's a plug in power cord.)

Take a low-scale DC voltmeter reading between the engine block and the ground tab on the shore power cord, boat end. 
ANY voltage at all and you have an offending neighbor. 

For your own boat, similar test but between the engine block and the on-board shore power (green) ground (cord disconnected as before). 

The more sensitive the voltmeter the better.

The snarky answer is look for the damned bond or test for continuity between the on board shore power ground (cord disconnected) and the engine block.  If it's there, the potential for stray current corrosion exists.  Actually, a thorough test would not be limited to the engine block.  All underwater metals should be tested as described above.