Carnauba wax vs. gel coat sealants

Carnauba wax vs gel coat sealants,
which is better?

    No one debates the need to seal and protect gel coat finishes but there is disagreement over how best to do it. Many "old salts" will only use a natural carnauba wax but boat manufacturers are increasingly recommending only gel coat sealants. There are a number of valid reasons for this. While carnauba waxes may be fine for fresh water, sail boats, their durability is very limited in salt water, especially on power boats. Combining the corrosive effects of salt water and the abrasion caused by the hull cutting through the water limits carnauba wax durability to 60 days or less. Above the water line is not much better. Carnauba waxes start to melt around 150 degrees f. Direct and reflected UV and thermal radiation is literally melting the wax off the finish.

    Synthetic sealants on the other hand, have better bonding characteristics than carnauba waxes, better abrasion resistance and melting points in the thousands of degrees. Synthetic sealants will outlast carnauba waxes and will typically produce a brighter shine. Sealants should last 180 days, even in salt water.

    So why the debate? In the early days of recreational boating, enthusiasts often applied over-the-counter, automotive sealants to their boat's gel coat. Many of these sealants contained strong petroleum solvents and/or coarse abrasives which actually accelerated gel coat oxidation. These enthusiasts were applying a "protective" sealant to their boat only to have it quickly turn a dull, chalky white. No wonder sealants got a bad image among early boaters! 

    Rule No. 1: Don't use automotive sealants or polishes on gel coat finishes. There are exceptions but if the manufacturer doesn't specifically recommend their product for gel coats, don't us it! Use only polishes and sealants that are designed for gel coats.

    Another problem shared by both carnauba waxes and automotive sealants has to do with the very nature of gel coats. Gel coat is porous. Seen under a microscope, your boat's flat, smooth gel coat surface is millions of tiny holes! These holes, or pores, fill with microscopic grime, marine scum and salt crystals which promote gel coat oxidation. Think of this oxidation as "plastic rust".  The contamination in the pores is eating away the gel coat from the inside, filling the pores with a dull, chalk. As the chalk fills more and more pores, the entire gel coat surface will take on a dull, whitish finish. Carnauba waxes and automotive sealants do not remove pre-existing micro-contamination in the pores. Worse, they seal the contamination in place where it continues to oxidize from the inside, under the protective wax.