Piers
Well-Known Member
When checking continuity between and anode and something to which it's bonded, is 0.2 ohms too high?
Anode continuity
- Thread starter Piers
- Start date
kashurst
Well-Known Member
probably not as the simple answer - long answer:
how good is your meter? can you zero the ohms readings when the contact probes are touched together?
0.2ohm between two parts actually contacting isn't good, however if you are measuring from the rudder to the actual anode there is quite a bit of wire and connections between the two and is probably fine. The voltage in galvanic action is about 0.8v and the current is very small through sea water so 0.2 ohm shouldn't be an issue. I have measured more ( 0.8ohm ) through shaft contact brushes and had no ill effects.
how good is your meter? can you zero the ohms readings when the contact probes are touched together?
0.2ohm between two parts actually contacting isn't good, however if you are measuring from the rudder to the actual anode there is quite a bit of wire and connections between the two and is probably fine. The voltage in galvanic action is about 0.8v and the current is very small through sea water so 0.2 ohm shouldn't be an issue. I have measured more ( 0.8ohm ) through shaft contact brushes and had no ill effects.
Piers
Well-Known Member
It's a good meter and yes it reads zero when the terminals are touched. I'll check the cabling and routing and advise. Thanks for the help.
QBhoy
Well-Known Member
Totally fine, in my opinion. You'd do well to get exactly 0 end to end on a 6" nail, if your meter is decent (fluke or similar)
VicS
Well-Known Member
I'd be very happy with a reading that low.
Elsewhere on the forums someone is struggling with 700 ohms between a hull anode and prop.
Piers
Well-Known Member
Yesterday was a good day in the enghine room.
To double check continuity, I borrowed a much more accurate meter and found all bondings and anodes to be less than 0.2 ohms, mostly between 0 and 0.1.
Furthermore, and as rceommended by super-engineer Dave of M&G (Guernsey) I used a small smear of Evinrude Johnson Triple Guard Grease on the brass plugs when re-inserting the engine and stabiliser oil cooler anodes. Result? All registered 0 impedence to ground. How good it that?
So, lessons learned - use a really good meter, and yes, it's OK to use the right grease when re-inserting the anodes to enable easier extraction as well as stopping the small amounts of metal to matal corrosion.
To double check continuity, I borrowed a much more accurate meter and found all bondings and anodes to be less than 0.2 ohms, mostly between 0 and 0.1.
Furthermore, and as rceommended by super-engineer Dave of M&G (Guernsey) I used a small smear of Evinrude Johnson Triple Guard Grease on the brass plugs when re-inserting the engine and stabiliser oil cooler anodes. Result? All registered 0 impedence to ground. How good it that?
So, lessons learned - use a really good meter, and yes, it's OK to use the right grease when re-inserting the anodes to enable easier extraction as well as stopping the small amounts of metal to matal corrosion.
jfm
Well-Known Member
great result piers and it's nice to know it has been checked and confirmed. I think you are way over egging the contribution of grease to all this though!
Out of curiosity, do Fleming bond all the seacocks back the hull anodes with cable?
Piers
Well-Known Member
Hi JFM, yes everything is bonded except the trim tabs which chew their own anodes like there's no tomorrow - 2 x 2.75kg per trim tab.
Me overplay? Never! Just surprised to find it's OK to use it and that it might just stop that small bit of corrosion.
Bandit
Well-Known Member
I had a problem on my boat this year and I have seen several boats where there are bonding issues with trim tabs where the hinge piece that is against the transom is not bonded but the main tab plate has a disc anode on it, the bonding across the hinge pin is not very good, I now have a stainless wire between the two ensuring continuity
