Teak deck sealing

[DwayneSpeer]

I have a teak deck on my 78 Flying Dutchman which I recaulk several seams yearly. I''ve been using a commercial polysulfide rubber caulk. I was wondering if anyone has good experience with anything else, such as 5200?

[GordMay]

3M “101" is a polysulfide deck sealant. You shouldn’t have to re-caulk yearly.
3M “5200" is a polyurethane sealant, not recommended for decks.

[RichH]

Best teak deck caulk nowadays is a single part oxime cure silicone rubber offered by "TeakDeckingSystems" .... also available from Jamestown Distributors: http://jamestowndistributors.com/product;part;54700;process;search;text;teak%20deck Needs an ''isolation'' strip in the bottom of the deck groove.

[GordMay]

I''m not specifically familiar with the TDS product, however, I’m not certain how valuable an “Oxime Cure” system would be in a deck sealant application. I don’t think the deck sealant should come in contact with (or close proximity to) any metals (susceptible to acetic acids) .

Acetoxy-cure silicones are one-part, solvent-free adhesives that react (catalyze) with moisture to form a thermoset elastomer with excellent flexibility at low temperatures and thermal resistance to 600̊F (316̊C). Upon cure, these adhesives produce acetic acid as a by-product, which can be corrosive to some materials.
Single part silicone sealers generally contain a cross-linking catalyst (such as a tin compound) that is activated upon exposure to moisture in the air.
Since the acetic acid is released during curing, it can attack the underlying substrate material. This can cause corrosion of certain metals and prevent the proper adhesion of the silicone. However, on other materials, the acid can etch the surface slightly and increase the adhesion. Aluminum is one such material. Copper and zinc, however, are
corroded by the acid. Thus brass and galvanized steel should not be used with silicones which release acid. Dissimilar metals can form electrolytic couples and corrode severely underneath a covering of acetic acid releasing silicone.

Oxime-Cure Silicones:
A catalyzed moisture cure system, Oxime-cure silicones are also one-part adhesives that react with moisture; however, they produce an oxime (alcohol methylethyl ketoxime) rather than acetic acid. This byproduct smells like latex paint. Consequently, their by-products do not corrode ferric substrates, and generate a less pungent odor than does acetic acid.

Neutral Cure
A condensation cure system which liberates no corrosive (to metals) by-products upon curing. Alkoxy/Alcohol cure systems (Oxime) are neutral cure.

Further Reading:

Dow Corning Construction Americas Technical Manual
http://www.dowcorning.com/content/publishedlit/62-1112a-01.pdf?DCWS=Construction&DCWSS=Weathersealing%20Pr oducts

Synthetic Rubber-Based Adhesive Sealants
From "The Practical Sailor Library - Volume IV - Do-It-Yourself Improvement Projects"
http://bosunsupplies.com/Sealants.cfm
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[TrueBlue]

My boat has full overlay, shiplap edge, teak planking on all topside decks. The planks are screwed & bunged directly to a solid fiberglass substrate, no coring & no leaks.

However, the prior owner applied a light colored stain over the teak. In some areas, the stain had broken the bond between caulking & teak and most caulking needs replacing. I have decided to recaulk all decking on the boat. While not a difficult project, it will be tedious.

I have done extensive research into the best materials and methods to do this job. All caulking will first need to be reefed out . . . in most cases this will be easy, other areas will require a modified reefing tool (bent & ground flat blade screwdriver). A two-part black polysulfide caulking is the preferred & best material for re-caulking. After replacing any loose/missing bungs and lightly sanding the teak surface, I will clean out the grooves with acetone. Blue painter''s tape will then be applied to both edges of each groove.

The caulk is mixed & pre-filled in hollow tubes and kept cool in an on-board refridge until needed. After caulking a designated area with a gun, a putty knife is used to smooth each seam flush with the tape. The tape should then be removed before caulking sets-up.

No caulking lasts forever, but this approach should be as close to permanent as you can get. Avoid the use of any single part caulk, since it simply will not last as long as two-part polysulfide.

Steve