REDZn Engine Anodes are now known as PRO Engine Anodes. Available exclusively at

FAQs & Tips

REDZn Tips


1. Keep your motor and your bilge dry

After closing the seacock, the raw water circuit is still flooded with seawater. To keep that seawater off your motor and out of your bilge, run a shop-vac as you unscrew the plugs. Push the hose right against the plug/cooler interface and as you slowly disengage the plug the water begins to weep out. You'll see the vacuum pull it right out of the cooler opening. Unscrew the plug further so the vacuum can suck more volume. Once the plug is removed push the vacuum hose against the plug opening. It will remove more water from the system as well as suck out any zinc “crumbs”. Once this is done at one or two spots, the raw water is generally gone from the system. Nothing to wipe up on the bilge floor and no salt water in the nooks and crannies of your motor.





1. What are the symbols on the sides of the plug heads?


The symbols on the sides of the plug heads are part codes designed to be easy to mark and easy to read in the limited space available on the plug head. The part codes make it easy to identify and reorder REDZn without having to consult your records or manuals or having to contact manufacturers to determine part numbers. See the 'Buyers Guide' page for the cross-reference table.


2. Can REDZn Engine Anode plugs be reused?

Each REDZn Engine Anode is a complete anode assembly. The plugs are not intended to be reused. See the 'Reuse' page for more information as well as item '2b' below.


2b. I don't like your answer to question '2', can I reuse the plugs anyway?


If you are willing to go through the effort of re-using the plugs, we are willing to support your effort – and the idea of keeping material out of landfills. See the bottom of the 'Reuse' page for more information.

3. Should I use thread sealant when installing REDZn ™?

REDZn use standard NPT threads. While there is some disagreement over this issue, it is the most common practice to NOT use thread sealant for engine anodes. For protection against galvanic corrosion, it is imperative that metal to metal (electrical) contact be maintained between the plug threads and engine component in which it is installed. In engine anode applications, healthy threads should seal with the plug “snugged” and no sealant. However, beware of over-tightening. The plugs are tapered and forcing the plug too far if it fails to seal will likely worsen the situation. If you are faced with a plug that won't completely seal, you can explore sealant, but note that sealants are generally non-conductive and can interfere with the required electrical contact. You must verify electrical continuity between the plug and the engine component with a multi-meter (if you aren't familiar with this it is straightforward – I promise- just search the web). I suggest keeping the sealant away from the first few threads nearest the opening to keep it out of the cooler. The subject of thread sealant on engine anodes is debated in various forums. For a detailed discussion check out the following link (as well as their other useful articles – no affiliation) and decide for yourself. Here at REDZn ™, we default to NOT using sealant.

The Myths & Realities of Using Pipe Dope on Threads - Seaboard Marine (

4. How much should I tighten REDZn anodes?

REDZn use standard NPT threads. There is much technical information on NPT threads, but most people tend to “use the force” when tightening. In engine anode applications, healthy threads should seal with the plug “snugged” and no sealant. If you have “snugged it” and it is not leaking - stop. Beware of over-tightening. The plugs are tapered and forcing the plug too far if it fails to seal will likely worsen the situation. For related information, see the FAQ on thread sealants. A common rule of thumb for tightening NPT thread is to first screw to hand-tight. Generally 3-5 turns by hand (to get fully seated...sometimes these “hand” turns may need light force from wrench). Then for 1/8-3/4 NPT 1.5-3.0 turns with wrench to seal and for larger sizes 1-2.5 turns with wrench to seal. I am an over-tightener – just can't help myself. For those with the same affliction, here's another warning - don't over do it! (or use a short wrench).


5. Do REDZn come in shapes other than hex head?


Currently all REDZn anodes are hex head. If you need square head or something else, please get in touch and we will try to help.

6. What size REDZn are available?

REDZn are currently available in various lengths for NPT plug sizes: 1/4, 3/8, 1/2 and 3/4 (please browse the store for details). Engineering for 1” NPT and 1¼” NPT sizes is complete, but we are not yet in production. If you are interested in these sizes, please contact us.

7. I need a different length, what should I do?


Sometimes the standard length anodes don't work for a given situation. I have this problem with my transmission coolers. Order the next size up and cut to length. Depending on the tools you have on hand, this can be hard or this can be easy. If you need a zinc or two cut down in length, give us a call, put a note in the order or send an email and we'll be happy trim it for you.

8. How is anode length measured?

The length of an anode is measured from the end of the rod to the where the rod meets the plug. In other words, the length of a zinc does not include the plug.

9. Does REDZn offer aluminum or magnesium anodes?

Currently we only offer “zinc zincs”. Magnesium for use in fresh water and more importantly aluminum for salt-water/brackish conditions are in our future plans. Aluminum is gaining in popularity as an anode material of choice for most conditions but the current market is overwhelmingly dominated by zinc. Please check back soon for the addition of “magnesium zincs” and “aluminum zincs” or, better yet, please contact us if you would like to nudge the process along.


10. Is it ok to use one anode material externally (running gear/hull/etc) and a different material internally (engine coolers, etc)?


A common example of this scenario would be aluminum externally and zinc pencil anodes in the motors. This is an acceptable configuration. An excellent resource on bonding systems that touches on this topic (2nd to last paragraph, search for ‘body of water’) can be found here:


Getting to Know Your Vessel – Bonding Systems and Corrosion Prevention | Steve D'Antonio Marine Consulting (


There is a wealth of authoritative technical information covering many topics on this website.

11. Why is there an O-ring or gap at the plug/rod interface and why did I receive some with an o-ring and some with just a gap?

There are several reasons for the rubber O-ring between the plug and the shoulder of the zinc rod. During early prototypes of REDZn the rubber O-ring was utilized to provide added stability to the rod. It also provides a physical barrier between the shoulder of the rod and the rim of the plug. This is a problem area in traditional threaded zincs as a “corrosion-weld” forms along this boundary fusing the plug and rod shoulder together. This fusion results in a failure mode where stuck rods break due to torsion upon removal. As REDZn anodes progressed to final production design, the stability need was greatly diminished. We are investigating whether that design element is still needed at all. Data thus far has shown that the problem of the “corrosion-weld” at the plug/rod shoulder interface is adequately addressed simply by an air gap between these two surfaces and test results on boats using REDZn with the O-ring removed have shown them to be equally reliable. Testing is ongoing, with the current intent being removal of the O-ring, but retaining an air-gap between the two surfaces.