Join Date: Jan 2008
Location: Seal Harbor, Maine
Thanked 21 Times in 20 Posts
Rep Power: 9
Re: Paint gelcoat
My deck is badly crazed and cracked, too. It is impossible to keep clean as all the tiny cracks either accumulate dust and dirt or provide a place for algae to grow. After winter storage it gets scrubbed with a stiff brush to make it look white again. I have followed that with onoff on occasion to get down into the micro cracks. It has a molded in texture, too. Half way through July the algae starts to show to me. There are couple of places where checking has "released" a small chip. I might repair these small spots and I might not. They would get "patched" with an epoxy paste or more gelcoat. I will use a simple rubber mold material to transfer the surface texture from a spot on the deck that is O.K. to the uncured paste repair. This can involve as much detail work as you want to expend. My deck is sound.
I am planning to refinish it. I have experience with coatings on yachts. I wrote and taught the course "Marine and Industrial Coatings" for the Maine State Marine Trades Center ("Boat School") in Eastport, Maine. 15 years of teaching and using a wide variety of epoxies and 2 part polyurethanes including Awlgrip is the experience base I will rely on for my own deck. One of the comments here, that Awlgrip is an epoxy, is not correct. It is a 2-part coating but its chemical properties are quite different from epoxy.
Surface prep is the bottom line for any finish job. Eliminating any chemical "dirt" comes first and last. Depending on the "adhesive" properties of the coating it can require a "tooth" to latch onto or may be capable of attaching to a fairly smooth surface because it is a good "adhesive". "Cohesive" properties are important, too. These are the bonds within the coating that bind it together to form a durable membrane on the substrate. Both 2-part epoxies and 2-part polyurethanes rate high in these qualities with the 2-part polyurethanes (Awlgrip) being better at both. Epoxies wear better. The additives to these resin systems give them the properties that define them as "high build", "primer", "high gloss", etc.
Sanding down all the texture is too much work and I don't feel it is necessary to achieve the fill / seal / finish I am looking for. A careful and safe cleaning of the old surface will suffice. A through wash down followed by "OnOff" and another wash down followed by a solvent cleaning ( An acetone wash followed by an alcohol rinse should be all it requires.) These are dangerous chemicals and a through understanding of their properties is required. They are hazardous and explosive! I was (am?) also a NIOSH trained and certified respirator fit tester and trainer. I have full face respirators and air supplied ones for enclosed spaces. The full face will suffice for this as I will be working outside under a tarp. Eye protection from these harsh chemicals is a must! Nitrile gloves too.
The only coating I intend to use is flattened Awlgrip applied with a solvent resistant roller. It will be thin enough to fill the small cracks and seal things up. I don't want a gloss finish and adding some flattener will improve its build. I will do a section at a time. I will likely apply a second coat to the first while it is still "wet" depending on how much filling the first coat achievies. Mix up the entire batch so it all matches then catalize only enough for the day's work. I expect the high spots to suffer some wear so I will try to match the off white Awlgrip with the gelcoat's color. I could use a thinned epoxy and would if I already had the paint to save the cost of buying Awlgrip. Epoxies tend to discolor as topcoats but their service and abrasion resistance are superior to polyurethanes. Either coating can be used as a primer or a topcoat. Understanding the prep of an epoxy as per Faster's post is essential and makes working with it, where cleaning is required down deep into small cracks, problematic.
If you have the need to remove the old surface and have the resolve, go for it. I am happy with the texture of the old gelcoat non skid. I just want it to look a bit cleaner. Filling the cracks that 30 years of curing and crosslinking cohesive forces have added to my deck's surface is my goal.
Last edited by downeast450; 01-04-2013 at 08:05 AM.