zinc wear
- Thread starter gettinthere
- Start date
Annapolis varies from 5-30% salinity, depending on the marina (some have a lot of fresh flow) and the time of year (late summer is higher). That makes a lot of sense. That would make the norther half of the Bay into Aluminum anode country, no?
Is there a down side? A question, not a challenge, since I can't think of one. The difference in voltage isn't enough to matter and some say they last longer at the same amperage.
I'm thinking about doing some long term testing, rather like the PS bottom paint testing, where I hang many zincs in the water (Ocean and Chesapeake) coupled to copper for a year, checking voltage and current before and after, and weight loss.
I've also heard some stores of bolt failures, which I assume are traceable to low quality SS and hydrogen.
Fastbottoms? Anyone?
In saltwater, zinc or aluminum- samey, samey, all same. Either are great. Just don't use both.
Again, the reason your zinc anodes crusted over is because you used them in fresh and/or brackish water, not because there is something inherently wrong with zinc anodes.
I didn't say there is anything wrong with zinc anodes, just that aluminum anodes work better, last longer, and cost less. I do know that a lot of boaters think zinc anodes are better because they "last for years"...not understanding that they long ago quit working.
Since I don't have a Max Prop, but did look at the design, I am guessing the added zinc on the hub is to extra protect your $1500 prop versus your $500 shaft.
The way many large vessel check their metal is an installed galvanic corrosion reference probe to continuously check their protection.
I bought one of these "portable probes" and once a month in my 24/7/365.25 waters I test my "shaft/prop/engine" protection.
http://www.boatzincs.com/corrosion-reference-electrode-specs.html
That is the way to check.
But...
Once you have experience with your zincs on YOUR boat, like you "getinthere" seem to have, you simply adjust the timing, size and mass of zinc to fit YOUR needs. Don't listen to the "Google Chemists" generalize with their sermons!
This is one of the best charts to compare why you can use several different sacrificial metal anodes to protect the more Nobel series metals.
http://www.corrosionist.com/galvanic_corrosion_chart.htm
Left side is very very slow corrosion, we just need gold or titanium prop and no zinc needed!!
Right side are the faster corroding metals. If you sailed in "distilled water" no corrosion. Magnesium works in salt water too, but you couldn't afford the cost due to it's disappearance rate. Please note that Magnesium is use to protect Aluminum engines and Zinc can't since Al is less Nobel than Zn.
Good Luck with pinpointing YOUR boats zinc needs!
Jim...
PS: Are you sure your Max Prop is not GOLD? Price says it is! LOL...
The way many large vessel check their metal is an installed galvanic corrosion reference probe to continuously check their protection.
I bought one of these "portable probes" and once a month in my 24/7/365.25 waters I test my "shaft/prop/engine" protection.
http://www.boatzincs.com/corrosion-reference-electrode-specs.html
That is the way to check.
But...
Once you have experience with your zincs on YOUR boat, like you "getinthere" seem to have, you simply adjust the timing, size and mass of zinc to fit YOUR needs. Don't listen to the "Google Chemists" generalize with their sermons!
This is one of the best charts to compare why you can use several different sacrificial metal anodes to protect the more Nobel series metals.
http://www.corrosionist.com/galvanic_corrosion_chart.htm
Left side is very very slow corrosion, we just need gold or titanium prop and no zinc needed!!
Right side are the faster corroding metals. If you sailed in "distilled water" no corrosion. Magnesium works in salt water too, but you couldn't afford the cost due to it's disappearance rate. Please note that Magnesium is use to protect Aluminum engines and Zinc can't since Al is less Nobel than Zn.
Good Luck with pinpointing YOUR boats zinc needs!
Jim...
PS: Are you sure your Max Prop is not GOLD? Price says it is! LOL...
This week I sold (and installed) an 18", 4-blade Max Prop "Easy" model on a Beneteau 423. My price to the customer for the prop alone was $3650, and that included a $300 markdown from the retail price.
More like 20% on a volume basis (same size zinc).
But yeah, a whole lot of Chesapeake zincs are crusty from the brackish water.
And pretty much every popular barrier island sound or estuary sailing venue in the continental US, Central, and South America. It would be interesting to know how many days of fresh / brackish flush it takes to salt-up a zinc and make it quit working.