Posted on Leave a comment

Does Volvo Neutra-Salt Really Work?

The Boundless Outfitters demo boat is a 2007 Regal 3760 Commodore with twin Volvo 8.1 gas engines that are raw water cooled (yikes!). This is considered to be terrible for boats used in brackish and salt water. Our boat came equipped with Volvo’s Neutra-Salt system installed for both engines. The engines are also equipped with fresh water flushing ports.

The Neutra Salt system is basically a tank with a solenoid valve that allows a small amount of the salt neutralizer to flow into the engine’s raw water cooling water system. The salt neutralizer is teed into the cooling hose prior to the raw water pump, so the solution is dispensed throughout the entire engine, manifolds, and risers. The instructions call for actuating the Neutra-Salt system for 45 seconds before turning off the engine. No fresh water flushing is needed.

I have asked engine repair shops about Neutra-Salt, and have not gotten good answers as to how effective the solution is. Neutra-Salt is expensive at over $50/gallon, so it better work! I decided to perform an experiment to determine the effectiveness, and whether another (cheaper) product could be a fair substitute.

Purpose:

To compare effectiveness of Neutra-Salt in brackish water solution and CRC Salt Terminator in brackish water solution, against fresh water flushing or doing nothing at all.

Setup:

Three sealed containers were filled with equal amounts of brackish water drawn from Lake Boca Raton. One sealed container was filled with the same amount of fresh water drawn from the boat’s tank. 

Two teaspoons of Volvo Neutra Salt was added to one container of brackish water.

Two teaspoons of CRC Salt Terminator was added to one container of brackish water.

One short length of one inch square steel tubing was added to each container.

Results:

After 24 hours, the containers were photographed with a flashlight shining to highlight the condition of the steel sample.

Fresh Water @ 24 Hours
Brackish Water @ 24 Hours
Salt Termator @ 24 Hours
Neutra-Salt @ 24 Hours

After 72 hours, the containers were photographed again in the same manner:

Fresh Water @ 72 Hours
Brackish Water @ 72 Hours
Salt Terminator @ 72 Hours
Neutra-Salt @ 72 Hours

Conclusion:

After three days, Volvo Neutra-Salt solution is the clear winner. The steel sample still looks perfectly rust free. The CRC Salt Terminator is somewhat effective, but not quite as effective as Neutra Salt.

I was surprised to see that the sample in fresh water has almost as much rust as the sample in untreated brackish water. That tells me that fresh water flushing has little effect, and is almost as bad as not flushing at all. 

Recommendation:

Based on this experiment, I strongly recommend the Volvo Neutra Salt system for every gas engine operated in salt water – even those with fresh water cooling. Exhaust manifolds are rarely fresh water cooled on gas engines, and don’t last long (typically 3-5 years). Replacement manifolds,  risers and elbows cost upwards of $2000 or more per engine. Using Neutra-Salt will extend the life of these costly components by a significant amount of time.

Further testing:

So far, this experiment has only been running for three days. I will keep it going for a few weeks and update this page. 

It would be interesting to determine whether using Neutra-Salt in engines that already have some rust will stop the decay. At the conclusion of the test I will move the sample from the untreated brackish water container to the Neutra Salt container to see what happens.

Follow Up:

After one week of soaking steel samples in the various solutions, the only noticeable changes were more oxidation on the three samples that were not in the Neutra Salt solution. Here are the photos:

Fresh Water @ One Week
Brackish Water @ One Week
Salt Terminator @ One Week
Neutra-Salt @ One Week

It is obvious that the Neutra-Salt from Volvo Penta is the clear winner. I am not a chemist, but something significant is happening to protect the steel sample from the ravages of aqueous salt solution.

Additional Test:

To learn how an engine that has already suffered some rust will respond to treatment with Neutra Salt, I moved the steel sample from the untreated brackish sample to the Neutra Salt solution, leaving in place the steel sample that had been there all week. After about 18 hours, I took photos:

Original Sample (Lower Left) Formerly Rusted Sample (Upper Right)

I could not believe my eyes! The formerly rusty sample is now clean as a whistle. You can see how the sample that was once rusted has softer edges. I left the raw edges from the cutoff wheel on all the steel samples, as can be seen on the sample at the lower part of the photo. I am truly amazed, and a believer in Volvo Penta’s Neutra Salt!

Posted on Leave a comment

Crevice Corrosion Can Ruin Your Watermaker!

You may have heard of Crevice Corrosion. Perhaps you  have confused it with galvanic corrosion (electrolysis), but the chemical process is quite different.

Without explaining all the chemistry (as some of it is beyond my Chemistry 201 studies!), I will explain what happens. Essentially, Crevice Corrosion occurs to Stainless Steels when in the presence of seawater that has been depleted of oxygen. How does this happen?

Seawater that is trapped against stainless steel equipment loses its oxygen over time by causing oxidation of the materials it is in contact with. Crevice corrosion does not require dissimilar metals to occur. In fact, it can even occur where a plastic part is clamped to a stainless steel part (or even painted stainless steel!), if seawater is allowed to become trapped between the parts.

The result looks a lot like galvanic corrosion, but is not caused by the same problems.

Common boating equipment that frequently suffers from crevice corrosion is trim tabs. I have seen trim tabs that have been properly maintained, with zincs replaced regularly, fall prey to crevice corrosion. This usually occurs between the hydraulic ram base and the tab itself. You should inspect yours, and always make sure that the components of your trim tabs are well bedded in a waterproof compound (3M 4200 or 5200 or similar adhesive). Don’t trust silicone for this critical task.

Another piece of equipment that we see suffering from crevice corrosion is your watermaker high-pressure pump and high-pressure fittings. This is due to inadequate fresh water flushing of your desalinator. Would you believe that some watermaker manufacturers still build systems with no easy method for fresh water flushing?

The potential for crevice corrosion is why I personally prefer Titanium Alloy or Nickel Aluminum Bronze (NAB) for high pressure watermaker pumps.

To learn more about crevice corrosion, please see this Wikipedia article on crevice corrosion.

Happy cruising!
Tim