restoring 1974 Sea Craft what primer paint to use?

I have been brought in to help my friend restore his Sea Craft. Most of the work has been done, some by me and some by another friend. The other friend replaced the floor, boxed in the transom, and built a custom center console. He used Coosa board for all with 1708 and polyester resin. He even did some faring with another polyester faring compound.

I came a week ago and have taken on the task of glassing on the cap. I used all epoxy resin with 1200 biax.

HOW DO I TIE ALL THIS TOGETHER? The boat is very rough and we have work done in polyester and epoxy. A lot of filler primer and blocking will be necessary. He does have a gallon of polyester primer that we can use over the areas repaired with poly, but where do we go after that? I could use a product like Awlgrip Hullguard, but IMO it does not sand easy. I need something that sands easily since there will be a lot of blocking out to get it straight. I like PPG K38, but I believe this is a LPU 2K primer and not sure how it will adhere?

I am thinking about sealing everything with an epoxy primer (maybe awlgrip 545 or a PPG primer), and then some thick coats of 2K filler primer like K38. Finally I will seal all that in with a sealer coat of epoxy primer before painting?
What are your thoughts?

 

Use an epoxy primer, if you don't want issues. I've seen and used other primers over the years, but have never had an issue with epoxy, though have with some others. For the initial coats, K38 (urethane) will work, but I still like the epoxies. Have a look at the PPG primers. High build for the blocking, then you can switch it a thinner finishing primer for the smoothing prep under top coat.

 

I like PPG also. What high build epoxy pri.er do you recomend?

So what I think you are saying g is that I can use the K38 and then seAl it with the epoxy primer, but what is even better is to simple use epoxy throughout? Plz give me some PPG product numbers, both for the high build and the sealer. Ty

 

You don't need a sealer, just a primer. I don't recommend multiple primers, unless you need a lot of blocking, at which point you'll want a high build first, which can be left alone or over coated with a thinner primer for finish work.

 

The boats pretty rough and needs a lot of blocking

We have decided to go with an epoxy primer, then a fill primer (G2 polyester primer). The boat has had a lot of new construction added, to include new stringers/bulkheads, floor, custom center console, the transom boxed in, etc. We also epoxied the cap on and then ran a couple of layer of 1200 biax over the deck to accommodate heavy foot traffic.

The guy at SPI was very informative and helpful. He said that epoxy primer is really not meant to be a high build, easy sanding primer. What he basically explained is that to get high build, fillers are added creating the build and a porous surface. The porous surface is what makes the blocking go faster. He explained that the porous surface however does not do a good job as a moisture barrier. Since it's a boat, moister barrier is especially important, so it makes since to go high build then cover the high build with an epoxy primer. The boat will never be in the water for more then a few hours at a time, so it will not be bottom painted.

I told him that we already had a gallon of Polyester primer, and he said it builds three times thicker then any primer he sells. That being the case, we are going to first cover everything with the epoxy (adhesion), followed by heavy coats (5 mils each) of the Polyester primer. Next will block out the polyester primer and re-apply where needed. Finally once everything is nice and straight we will do a last coat of epoxy and lightly sand the epoxy with 320 or 400 before painting.

Plz let me know if you think this is a good idea?

 

The paint guy was blowing smoke in non-speaking orifices, possibly to sound like he knew more than he actually does.

All primers, including epoxies have fillers, usually several. Some (the high builds) have more fillers and often different types. Epoxies can be easy to sand, though you should get the blocking done in the first 3 days after coating, or some can tend to get much harder to sand. You've already got a sealed surface with the biax and epoxy. A moisture barrier is important, but not so much on a deck or topsides as it is on the bottom (immersed). Good quality top coat will effectively seal the surface, particularly if over a good quality epoxy primer, that is also over an epoxy coated and sheathed substrate.

Personally I don't fool with polyester primers any more. I use a regular epoxy primer if the work is ready to finish, but if it needs heavy blocking, I use a blocking primer (also epoxy). This is the situation with you, though you already have polyester on hand. For no compatibility issues, I'd just stick with what you have and block out with it, then put more polyester over it, to seal and prep for finish smoothing. I've never seen issues with two quality epoxy/polyester primers over each other, but the chemistry says there's a potential for it, which is why I suggest all epoxy or all polyester.

 

Can you PM me with a recommendation.

PAR, what you are saying makes since, however it is difficult to find high build epoxy in the auto paint industry. The only high build epoxy I have seen is the Awlgrip Hull Guard. In the auto world it seems that when people want High build, they go with a 2K primer. The paint guy I spoke to doesn't deal with Polyester primer (he sells a regular epoxy and 2K primers). He said the polyester fills way better then anything he sells. That is what is so attractive to us. High build with easy sanding, sounds like a perfect combo. Do you know how the build characteristics of the high build epoxy primer compares to the poly? Are there other high build epoxy primer besides Awlgrip Hullguard? If so what are they? It sounds like the safest bet would be to stick with epoxy primer and epoxy faring putty throughout the whole project?

 

The automotive industry is married to the latest 2K products being offered, so you'll see lots of polyurethane primers. The 2k's are now broken down into two major groups the acrylic urethanes and the polyurethanes. Chemically they're similar, from a molecular view, though they react differently and have some different elements, but are "related" chemically. The 2k's are polyurethane or acrylic urethane. The polyurethanes are now broken into waterborne and solvent based. The automotive industry is swinging toward the water borne stuff, because of VOC's and other concerns, but the solvent based stuff is still very common.

Generally, the acrylic urethanes are more flexible, dry faster and buff out easier, but not quite as tough as the polyurethanes (solvent base). Without getting into a dissertation on paint chemistry, you're best advised to work with the products you're familiar with. My worst results are with new products I didn't have a "feel" for yet. They're all a learning curve of some degree, so I tend to stick with what I know works. Since you're used to working with the solvent based LPU's, you should stick with these, for predictable results.

On a boat, I (again) tend to stick with epoxy putties and primers, mostly because I know their performance and physical properties, plus they seems to be a little better than the other offerings in the marine industry. The automotive industry still likes the poly's. For example the first acrylic I squirted, I had trouble. Normally I'd lay down a nice wet coat and see what was going on, but when I started, the opaque nature of the clear, caused me to over squirt. I later discovered it's a lot easier to buff out the acrylics, which turned out to be handy. I also had a hard time with drying, because I was in a down draft booth, which is fine for the solvent LPU's, but not the acrylics, which need oscillating air movement. It took two hours to dry, but in an upgraded booth would have been 15 minutes. This what I mean about sticking with what I know. If you want to experiment with new materials and processes, well . . . on the other hand I prefer predictable.

From a marine durability point of view, the epoxies (primers and putties) are tougher and can take any top coat chemistry. The LPU's are just as tough, but most of the time are coupled with polyurethane fillers, which aren't as tough in the marine environment, so to directly answer you, yep, an all epoxy (primer/filler) approuch is best (topped with a solvent LPU), but availability and familiarity come to play, which is the real decision IMO.

 

Not had any real problems putting PPG Kobe Hi build 2k poly/acrylic on top of epoxy sheathed or painted surfaces personally. The PPG cuts a a lot faster and will fill any small pinholes well. However the real 'sealing' is done by the original sheathing and/or epoxy primer. On internal tanks I have tended towards epoxy primer only whereas trying to get a good build for external hull surfaces it can be easier to multi layer build in all 2k stuff.

Half the battle is cutting at the right time re cured state. This helps get a good fine abraded surface for whatever is the next coat. There can be issues with paint expansion and contraction on larger projects, say 10 meters plus which may require an additive in the paint re the PU/acrylics.

 

Suki, thank you for weighing in. I was hoping to get steered in one direction or the other, but like everything else there is more then one way to do things and ultimately I have to decide.
I understand what PAR is saying about epoxy primer having the ability to be build primers. I just can't help but wonder why there are not more companies selling a high build epoxy primer? There has to be a reason. There must be a thousand different companies selling 2K build primers, but only one company marketing an epoxy as high build?

For decades the auto industry has recommended an epoxy over bare metal, then bondo (polyester putty), then 2K primer and finally paint (usually a LPU). Why is the marine industry any different when it comes to above the waterline? The inside of my boat is not going to get any more wet then my car. Here in Florida I talked to a boat builder who uses gel coat as his primer. It's inexpensive and fills well.

So why are there no hot rod enthusiasts using high build epoxy primers, and epoxy faring compounds on their classic car restoration? It also seems like the auto industry has gotten away from the "slick sand" Polyester primers in favor of the 2K even though a guy that makes paint says it builds 2 to 3 times thicker then any 2K he sells. The Polyester primer is also ready to sand in an hour or so, where the epoxy needs much more time to begin sanding.

Maybe the Polyester primers have lost favorability because of issue like hardening in the gun after 30 minutes? When I used it as a kid 30 years ago, I thought it was awesome. The only other primer that impressed me more was K200. Now that formula is not available and the K38 will cost a hobbyist like me a small fortune.

I don't mean to beat a dead horse, and I am weighing everyone opinion here. I respect and appreciate everyone's opinion so far. I am not trying to change the world, I just don't want my buddies boat to have a paint chip come off two years from now because I went one route over the other. So if there is anyone else who would like to weigh in, plz do so?

 

The epoxies are harder to formulate and base material costs are higher, so margins are less, for comparatively priced products.

I agree with everything you've said in relation to the automotive industry, but you do need to recognize they're also under a much stricter EPA and other agency oversight, so they're hoop jumping is more significant. They have learned (the hard way, remember the early 90's) to use epoxy bases under their 2k's. Polyester fillers do work for them, because they're not in the marine environment, which has a much high water vapor penetration than a car does. Even the top sides of a boat is living in a constantly 100% humidity condition, if berthed. Cars don't see this very often and all you have to do is go down to the beach and look at cars the locals own. They all have rusting issues, if they're fairly close to the beach or parked under a carport on a river. This is the polyester filler, which absorbs moisture, unlike the epoxies.

There are marine primers that are epoxy based and good building. You can also improve bulking with fillers, though this takes some experience to get right. I add bulking agents occasionally, but only on projects with lots of hollows and blocking. For average work, you'll get by with the usual suspects.

Look into MarPro Protect 70, AwlGrip D8002Q, Pettit 4700 and similar products. Some are designed as high build barrier coats, but for your needs will do fine. All the major formulator seem to offer something, but don't expect the automotive store to know what they are. Basically just look at "solids content" and pick the one with the highest number.

 

Speaking from a car restoration point of view, we tried to do everything in original type sheet metal via welding. Make sure it is rust free, and if filler has to be used we use a little epoxy not polyester. Reasons are many. As Par said, poly absorbs water over time and the rust forms quicker, it doesn't bond as well to steel. And even more important it is less flexible, it could cracked over time.
But again unless you are working on a corvette the base material is steel. On a boat your base is what? Your water absorbing could be happening from the other side because your whole boat is polyester.

 

We bought two gallons of Epoxy primer and sealed the boat. It had a decent build, but much harder to block then 2K. After blocking the epoxy, I'd say only a quart of the two gallon kit remained on the boat and many areas were sanded through, so the epoxy I laid down, didn't provide a moisture barrier anyway. In retrospect, I probably would have applied the 2k primer directly over the epoxy primer, blocked that several times and then another layer of epoxy before the Awlgrip.

The only reason I blocked the epoxy, is because the manufacture said it had a decent build and that we might be able to cover the imperfections just with the epoxy. IMO, I think it is possible staying with just epoxy primer, but you better have a nice palm sander , lots of disc, time and epoxy primer. The 2K sands so much better. The epoxy primer we used was not marketed as a "High Build". If we had purchased a "high build" epoxy primer then perhaps that would have been the way to go? I know a lot of boat restoration guys apply the "hi build" epoxy primer with a roller so they get 100% transfer rate. Perhaps that may have been the way to go?

 

Epoxy primer doesn't provide a moisture barrier. Yep, a real high build epoxy would do better or conversely you can add silica and make your own, though some experimenting will be necessary understandably. The 2K sands better, because it doesn't have as high a solids content. I spray high build on bigger jobs and roll on smaller.

 

I painted the boat last week. The hull from chime to rub rail were painted ICE BLUE and everything else was painted with Awlgrip Cloud white. The ICE BLUE was brand new paint, but we got a gallon of the cloud white from a friend. The white has completely faded and flattened out. The ice blue still looks glossy. The white now looks like is out of a spray can of flat enamel. Any clues as to why this would happen. We used the same converter and reducer on both the blue and the white.