An observation on hull paint

Discussion in 'Boatbuilding' started by Salmoneyes, Sep 11, 2018.

  1. Salmoneyes
    Joined: Sep 2018
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    Salmoneyes Junior Member

    If this is the wrong forum, Id be happy to move it..

    So, Im rebuilding a 36 year old steel ketch.... It was bottom blasted and painted in 2012..
    Today I had to grind some paint prior to making inspection cutouts in the keel.

    The paint in many areas had minimal to no adhesion. If you look close at the photo on the left, it looks like pitting. It is actually areas that the paint fell out. I believe it to be a moisture problem.. This was sprayed on, and it is possible by the looks that there was contaminates in the hose, air tank ???? Something to consider when having your steel hull painted in a boat yard. Consider the condition of their equipment, time of year, humidity, experience of the yard, and more importantly of the person applying....


    [​IMG] IMG_3114.JPG [​IMG]
     

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  2. Mr Efficiency
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    Mr Efficiency Senior Member

    Was there bubbling visible ?
     
  3. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    My 25 years as an industrial painter vote is for high build primer used bellow eaterli. This is a paint film break down issue, not an adhesion failure between layers of paint. If you could locate the fall out pellets, the dark blue would still be attached

    Oil/water contamination causes immediate fisheye, not delayed blistering.

    Another lickly culprit is epoxy primer killed by UV because of delayed topcoating.

    Five years is a long time between bottom painting.

    This is a good example that paint failure can be avoided by:
    +wise selection of materials
    +using good equipment
    +staying with environmental window
    +frequent inspection
     
  4. Salmoneyes
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    Salmoneyes Junior Member

    I wasn't looking that hard. I power washed the hull just enough to satisfy the requirement before hauling. The hull looked like a basketball surface. Highs and lows everywhere. When I hit it with the sander, it came off very easy. I have sanded many hulls and can not remember one being that easy.
    Look at the paint log, and specificly the humidy during the primer coat. That time of year it can cycle from sunny to foggy several times a day.
     
  5. Salmoneyes
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    Salmoneyes Junior Member

    Only the painter would know if it was immediate I think. What im seeing is the Amercoat 302 is not stuck to the metal hull, in what looks like water spots. I tried to add a photo of it but
    it isn't clear in the photo. But here it is...
    IMG_3116.JPG

    The owner died 2 years ago. The boat never left the marina after that paint job.

     
  6. Blueknarr
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    Blueknarr Senior Member

    Not all spots are on leopards.

    The spots in you pic are irregularity shaped and have sharp edges. If you enlarged the side profile it would appear as a cliff with 90° corners at the top and bottom. This can only happen if the flaw was created after the paint cured.

    The dark blue and white layers were penetrated by water. It collected between light blue and white layers. The dark blue was sufficiently flexible to expand as osmosis continued. The white layer is brittle and cracked. Many high build primers contain talc as the bulking agent; it is highly hydrolithic so will readily absorb large quantities of water. The amount of binder/resin/glue in the primer is reduced to make room for the additional solids causing it to be weaker than regular primers. Epoxy primers are usually waterproof; but UV creates micro fissures which allow water to pass.

    Contamination fisheye form in wet paint. The paint moves away from the water/oil/silicon leaving a perfectly round void with edge cliffs which are rounded off at the top and base. If they are painted over the top color fills in the pit. You would see a white layer with perfectly round dark blue spots.

    Painter error certainly will reduce the coating's lifespan. Five years under water is not premature failure. The blisters developed after the paint cured and vessel placed back into water.
    fisheyeexample.jpg
    This is typical fisheye. Notice how the pits are circular with eased edges.
     
    Last edited: Sep 12, 2018
    fallguy likes this.
  7. Salmoneyes
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    Salmoneyes Junior Member

    Blueknarr,,, interesting....

    Since we plan to do all our own painting, I want to insure that every step is correct in every way. I always knew that paint is the 1st line of defence against rust on steel... Since we plan to put everything into this boat, it has to last.
     
  8. Blueknarr
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    Blueknarr Senior Member

    some coating failures are easier to diagnose than others.
    Today's fun
    15367788377421885952942.jpg
    The previous painter did some things right.
    • Where you exposed the metal, it looks evenly blasted
    • Steal blackened by anti-corrosive chemical reaction
    • Corosion inhibiting layer of primer (red)
    Changes I would recommend
    • Neat unaltered epoxy has better adhesion and waterproofing than epoxy diluted into primers
    • Because of its inherent weakness and water absorption, high build primers should not be used bellow waterline
    Remember modern paint systems can have a twenty plus years lifespan above deck. Full time immersion shortens it to only a few years.
     
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  9. Salmoneyes
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    Salmoneyes Junior Member

    There are a slew of products out there. I have been speaking with both of these companies regarding their epoxy fillers for the pitting issues. They both offered up coatings for below the water line, which both have amazing clains. These are twice as much as the typical paint systems available, however they claim more than twice the life in the submerged environment.

    Our build concept is based on long term. If 10 years life is double the cost of a 5 year life, we will spend the extra for 10. Our concern is the potential for over exaggerated claims..

    FYI,,, I enjoy speaking with the Belzona rep and am leaning towards their products....

    https://static1.squarespace.com/sta...6839ab9dd5f29c2/1509100026685/chemclad_sc.pdf
    Belzona 1331 spray or brush applied coating https://www.belzona.com/en/products/1000/1331.aspx
     
  10. Blueknarr
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    Blueknarr Senior Member

    I read both sales brochures. I am not familiar with either company or product, so the following is based primarily on those brochures.

    Our concern is the potential for over exaggerated claims..
    The ChemClad did not identify its binder (glue). Only saying is was a polymer. The only paint I know of that may not be polymeric is used to decorate children's faces at fun fairs. Without knowing what polymer is used, I cannot determine if performance claims are lickly or exaggerated.

    FYI,,, I enjoy speaking with the Belzona rep and am leaning towards their products....
    That their rep is willing to spend time answering your questions is reason enough to seriously consider their product. It was identified as an 'epoxy with ceramic like fortification and no solvents'. I interpret this as undiluted epoxy with added silica. It should perform as advertised.

    People often complain about the cost is name brand resin and paint products sold in chandleries. I know that corporal products can be obtained elsewhere for less. However, they rarely come with the excellent tech support supplied by West Systems, Awlgrip or Pettit.


    https://static1.squarespace.com/sta...6839ab9dd5f29c2/1509100026685/chemclad_sc.pdf
    Belzona 1331 spray or brush applied coating https://www.belzona.com/en/products/1000/1331.aspx[/QUOTE]
     
  11. Salmoneyes
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    Salmoneyes Junior Member

    Blueknarr
    Seems like this is in your wheelhouse...

    Im learning that the paint system is very critical from product to application and if its under water, there is little margin for error, unless you do not mind doing it often.
    Im not concerned about biocide and all the controversy there. I am however interested in the best system and process for the hull paint (short of hot applied zinc).
     
  12. fallguy
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    fallguy Senior Member

    I wonder if I could do a small, tiny hijack? If you have fisheyes on some spots on an application on the bottom, what can you use to fill them to avoid removing the entire layer of paint. Is fairing compound the only option, or is neat epoxy a better solution?
     
  13. Salmoneyes
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    Salmoneyes Junior Member

    sounds like a good question to me...
     
  14. Blueknarr
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    Blueknarr Senior Member


    What a dark and twisting rabbit hole you send me down

    Depends demands depends
    Doubt removing an entire layer would ever be warranted. Spot sand, fair repaint.

    Was fisheye caused by surface contamination or applicator contamination.

    If dimples occur in a discreet zone then surface contamination is most lickly cause. Contaminants must be removed or fisheye will return.

    If dimples dispersed then the contamination came thru the applicator and doesn't need to be removed from surface. The pits can be immediately filled.

    Choice of filler depends of size of dimple and type of coating affected. Obviously clear coats need special treatment. Often I use a drop of paint applied with a toothpick or tiny brush. Most dimples are small enough that neat epoxy should fill them. Larger ones can be filled with fairing compound. 3M makes a filler specifically for minor surface pitting or scratches. It comes in a toothpaste tube and is safe for use above the waterline. Immersed areas should be filled with an epoxy based compound.

    I hope I have brought more clarity than confusion
     

  15. Salmoneyes
    Joined: Sep 2018
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    Salmoneyes Junior Member

    I think everyone agrees paint is the first line of defence against rust and corrosion on every surface of a steel hull. With so many factors having a potential negative impact on longevity, I would think by now, we would have some easier solutions.

    Even if you do everything right, from product choice to application, you still have to be concerned about compromising damages from floating objects, poor docking, and worse yet, hit and runs in marinas.

    I choose steel for piece of mind, but paint is going to cause me to lose sleep i'm sure....
     
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