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What sticks to #3?


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Hi All,

 

Just wondering if anyone can tell me what sticks to old (90s) Altex #3? I know some top coats didnt stick well to it (mine didnt in places) but what about other primers?

I have sanded it back a fair way with 150 grit and am hoping to apply another primer or undercoat over top of the #3 prior then top coating over that.

I was thinking YRA600, Interprotect or Durepox. Preferably the YRA as I already have a job lot of the stuff, if it will stick to it.

 

Also I read in a past topic that #3 prefers to be overcoated soon after sanding. Does this still apply to paint that has been on the boat for 25yrs?

 

Thanks

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As long as the 3 is adhering well to the Hull (Remember, even if you apply the best sticking, hardest wearing paint ever made, it will only ever be as good as what it is painted onto) then any 2 pot under coat will be fine.
However, 150 grit is far too fine. You want to provide a "key" sanding the surface with 80 grit at least.
What ever system you are going to go with, read the specs on it and it should tell you what you need to know in the way of prep work and what first to apply for what material it is you are painting.
Also, be careful when painting on Epoxies like say Durapox. Epoxies may work well, but can be a headache to sand and paint again in the future. Some like Durapox go so darn hard, they are hard to sand and hard to get anything to adhere again without a lot of hard elbow work keying the surface.
 

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Thanks, I would like to avoid using durepox or interprotect if I can as this will add another step and because it is difficult to sand. The #3 has stuck very well and looks to be in great condition. I just want to be sure that the YRA600 will stick to it. I might try giving international a call just to make sure.

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80 grit is what you need to prep hull. If you take to it with 80 grit it won't take long to remove all the previous coat of antifoul. I use a hard antifoul and make a point of removing the previous coat every year to prevent a buildup.

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its all above water line. Above post is in regards to my cockpit. Not sure whats on the hull yet, I havnt started sanding that. Theres no sign of any problems with the substrate on that though.

So as I understand it #3 three makes a good primer but a lousy undercoat. It sounds like its just the topcoat that doesnt want to stick to it, maybe cause there is very little mechanical keying with super fine sanding prior to top coating. I imagine it worked ok if topcoated within a day or two of original application to take advantage of chemical bonding.

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Hi Winter, I sanded as much #3 off as I could, then YRA over the top. For the most part it has worked fine, there is the odd bit smaller than a finger nail that didnt stick. This could have been down to prep though (but I was pretty particular about the prep). If you are going over #3 and the area you are painting is easy to sand and doesnt have too many coves, rounds etc then I would highly recommend 80grit, then interprotect, then 120 grit then undercoat of choice then top coat. I had some dramas with the hull and had to scrape off my finished paint and start again using interprotect as the substrate then YRA. Not fun.

I have heard good things about 545, the country was out of stock of 545 when I was doing my boat or I would have used it and saved a whole lot of sanding as it works as primer and undercoat.

All worth it in the end, over a year later and it looks like it was painted yesterday.

I hope this helps.

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I'm about to tackle this. 

Awlgrip rep said that 545 wont stick to the #3.  Wants me to to Interprotect first, then 545, then Awlgrip. 

I've no experience with interprotect but i'm not sure I want to learn to sand that on all the details of my cockpit etc...

 

4 Quotes from 4 reputable marine painters, none of them suggested using interprotect. Most of them said they would use 545. 

The Awlgrip rep says it wont stick,  and they are just re-doing a yacht whos 545 didn't stick to old #3. 

Who do I believe?

 

How bad is it to sand the interprotect? 

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Interprotect worked for me, I waited a day and a half to sand it and this was half a day too long, it was a painful long boarding job. The problem is you will not know that it hasnt worked untill after the top coat is on and the boat has seen some sunshine.

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