The issue of severe zinc scaling

B

baz

Well-known member
Joined
Jun 19, 2009
Messages
6,083
Fluid Motion Model
C-24 C
When I examine my Yanmar 4BY2-150 engine zincs after they have been in the engine for around 9 months I see that they are heavily scaled. Typically the scale material is a dull white in color and extremely hard and somewhat brittle. The scaling amount I've come across is close to 1/16" thick as best I ca measure it.

This brings me to the issue of scaling on underwater zincs for being affective once severe scaling thickness covers the zinc's surface area. I've not seen this to be a problem on the prop zinc nor the thruster zincs so far as the scaling seems to be non existent.

However, I have a large transom zinc plate (6"x8"), trim tab zincs and large ball zincs clamped to each of the swim step bracing legs. Scaling on these zincs is quite apparent.

I know that painting over say the trim tab zincs will make those zincs ineffective, so I'm thinking scaling will have the same affect.

I notice that the engine zincs if badly scaled can at times can be misleading in this respect as the zinc material can be eaten away internally even though scaled. This is evident by squeezing a badly scaled engine zinc between thumb and a finger and for it to completely collapse.

So I'm a little confused about concluding that badly scaled zincs are truly ineffective.

What are your thoughts ?
 
Brian: Thanks... Interesting -- that clears that one up. 🙂
 
Barry:

A couple of additional thoughts and or questions. Is the scaling light in color, like an oxidation? If so running a wire brush over the zincs takes this off but as Brian B's link from Boatzincs points out this is normal.....if it is the light colored/shaded scaling. On the other hand if the scaling is as severe as you state could you possibly have aluminum or magnesium zincs instead of zinc zinc's. There are zincs made from these three metals and each has a different scenario that makes one better to use then the other. For most of us in salt water with a boat that has shore power the zinc is best suited vs the aluminum or magnesium. The link that Brian B put up below refers to some charts that highlight the differences. Could you have non zinc zinc's? Here's the link that Brian B provided. Click on Q15 and you'll see two pdf files you can open to review what zinc's to use. http://www.boatzincs.com/faqs.html

The wrong zinc material may not be your problem but I thought it was worth exploring.

Jim F
 
Jim F: Thanks for that additional info... also very interesting stuff. The engine zincs I removed the other day were ones that the Gallery Marine Yanmar servicing company installed when performing the 250 hr maintenance last year for me. During that servicing I noted the zincs used were bone fide Yanmar packaged zincs that included bolt head, copper washer and integral pencil zincs. I have to assume they were the proper type.

Looking at the anode can one tell just from the color of the anode if its zinc, magnesium or aluminum ?
 
I don't think I could tell the difference maybe someone with additional knowledge could help us on this.

Jim
 
You must log in or register to reply here.

  • Tugnuts.com is the community hub for Ranger Tug, Cutwater, and Solara owners. Since its inception in 2008, the Tugnuts forum has grown into an active and thriving community of more than 9,000 members. It serves as both a meeting place for the best boating community online, and an invaluable archive of information.

  • User menu
Back
Top