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Boeshield T-9 - And Plain Old Vaseline - Our First Choices In Rust Preventatives... So Far

The fact that iron and steel rust comes as no surprise at all to boat owners. Most of the metal objects found on boats are made of corrosion-resistant metals and alloys. Most, but not all. There are still steel tools, plated steel accessories and steel engine parts to be found on almost any boat. If these aren't protected somehow, they will wind up as rusty steel tools, accessories and engine parts in very short order.

The Quest
The quest for a perfect rust preventive started, we'd guess, about two days after early man learned to smelt iron and it's still going on. There have been many approaches, ranging from plating or painting to coating the iron or steel part with a layer of heavy grease. All of these approaches rely on the same idea. Since rust is the product of iron's reaction with oxygen in the air, and since the process is speeded up greatly by the presence of water, rust can be prevented by coating the iron surface with a material that blocks out the air and water.
If all you're trying to do is prevent rust, any of the barrier-type products work fine. If you add the requirements that the rust preventive must be easy to apply, must last a reasonable time, and should not interfere with the functioning of the part that's being protected, the problem becomes more difficult. That hasn't stopped a host of companies from marketing dozens of different solutions.

When We
When we set out to test rust preventives, we quickly realized that boaters weren't the only ones concerned. Everyone we talked to, it seemed, had a favorite product that worked better than anything else on the market. We wound up with a dizzying collection of no less than 25 products, from hardware stores, sporting goods and firearm dealers, as well as marine chandlers.
All the products we tested claim to prevent rust. Most claim one or more additional capabilities-lubrication, cleaning, penetration, the ability to free frozen nuts and bolts, and so forth. Many also claim to disperse or emulsify water, and some are said to dry out wet ignition components. We decided to limit ourselves to testing them solely as rust preventives here. A second test of penetrants and compounds intended for use in a galvanic environment is currently under way.

The Tests
Our tests were simple, direct, and severe. First we prepared identical 1 by 6 inch carbon steel strips, degreased them, and polished them bright. These were treated with the various products, following the label instructions, carefully keeping the treatments separated to avoid cross-contamination. Each strip was identified by stamped in numbers indicating which product it had been treated with, and which set of test conditions it was to undergo. (We stamped the numbers into the metal because most of the products did an excellent job of dissolving "permanent" marker pen ink.)
We tried each product under three test conditions: a) exposed to repeated cycles of saltwater immersion and salt-air exposure, done by hanging the test strips from a dock one foot below the high-tide mark; b) exposed to freshwater "rain" for five hours per day; and c) exposed only to salt air by suspending them about 3 feet above the high-tide mark on the dock. We continued each test until at least some of the strips had rusted.

What We Found
Clearly, the intermittent immersion test was the most severe of the three. After six days (12 immersions), only four products- Brownell's LTS-1, Pachmayr Rust Preventative, RIG Universal, and plain old Vaseline Petroleum Jelly provided sufficient protection so that no rust appeared on the steel strips. Two more, those protected with Outers Metal Seal and Boeshield T-9®, showed only very slight traces of rust. Most of the others were badly rusted.
After four days, the freshwater test demonstrated clear differences in the effectiveness of the various rust-blockers under non-salt water conditions. The strips treated with Brownell's LTS-1, Outers Metal Seal, Pachmayr Rust Preventative. and Vaseline showed no signs of rust; those with ACF- 50, Boeshield T-9®, Hoppe's Gun Grease, and RIG Universal had only very slight traces. The rest exhibited a range of rusting from slight to considerable.
The salt-air exposure test didn't produce the dramatic differences we obtained with the other two tests, but the top six products in the previous test also scored well in this one. While some products that performed poorly in the other tests did well in this less severe exposure, the results we obtained generally confirmed our findings in the other two tests.

Recommendations/Conclusions
It's clear to us that the six products that stood up best in both the intermittent-saltwater-immersion and the freshwater "rain" tests will provide the best rust protection. Rust protection, though, isn't everything. RIG Universal and Vaseline are both greases, which limits their usefulness somewhat. Both leave a greasy film, even after wiping, that can act like a magnet for dirt. Of the greases, Vaseline was rated excellent, and RIG Universal was very good. Vaseline cost us about 12 cents an ounce, while an ounce of RIG Universal cost a buck a pretty clear factor in favor of Vaseline (or other generic petroleum jelly). Brownell's LTS-1 is a fairly thick liquid that is normally brushed onto a surface, although it can also be thinned and sprayed. It dries to a tough, brown colored film. Its performance as a rust preventive was rated excellent. We believe, however, that Brownell's LTS-1, as well as RIG Universal and Vaseline, are best suited for steel items that are being stored, rather than those in actual use.

Boeshield T-9®, Outers Metal Seal, and Pachmayr Rust Preventative are all packaged in aerosol spray cans the most convenient form and all dry to a thin, virtually invisible non sticky film. All three will leave a steel article in ready-to-use condition, though Pachmayr's performance in our tests was excellent, while the other two were rated very good. Pachmayr was also the priciest of all 25 products in our test, costing a stiff $2.08 per ounce.
Both Outers Metal Seal and Boeshield T-9® are priced below the average of products in our test, and either will do an acceptable job of preventing rust. Of the two, Outers is the more difficult to find; Boeshield T-9® is available in most marine-supply outlets. It would be our first choice for most on-board uses. We'll test it against other penetrants in our next round of testing.

Our test of greases, oils and aerosols finds Boeshield T-9® and good old Vaseline are best buys in protecting metal brightwork.