Coating SS components crevice pitting

Discussion in 'Boat Design' started by abosely, Jun 23, 2023.

  1. abosely
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    abosely Senior Member

    If 304 or 316 stainless steel is completely coated & encapsulated like coating with Cerakote H Series baked coating.

    If the SS part or component is completely coated with Cerakote, oxygen would be blocked from contacting the surfaces on the SS part/component.

    If the part/component is used on a boat in saltwater, would that potentially cause pitting/crevice pitting?

    Reason for coating with Cerakote H Series would be to have SS part/component but want durable color coating.

    From what I understand, if either a coating or burying SS component in wood or epoxy that blocks oxygen from SS surfaces, will most likely eventually causing corrosion pitting.
    Or am I missing something?

    Confusing because SS is chrome plated and seems to be ok, but maybe not used in saltwater environment?

    Cheers, Allen
     
  2. comfisherman
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    comfisherman Senior Member

    Have seen really bad corrosion with 304 below the waterline not nearly as much with quality grade 316 (reputable sourced 316). Considered cerakote for my rudder that was 316 but didn't really want to try and make an oven to fit it.

    Coating some small stuff and my hydraulic bank in absolute black, and have coated tons of 4140 but it never went below the waterline...
     
  3. Ad Hoc
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    Ad Hoc Naval Architect

    That's not strictly correct.
    This is crevice corrosion, as that occurs when there is a definite shielding of the oxide layer, thus starving the metal of oxygen. Such as under a bolt head of washer.
    Pitting can take place in open exposed surface, as soon as the oxide layer is broken, it just requires a more corrosive environment. A higher salt content is the initiator, in this sense.
     
  4. jehardiman
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    jehardiman Senior Member

    Adding to Ad Hoc's comments...is there a reason you want a coating? For what? Just colour?
    As was stated, it is the crevice that is the issue. There are decades of successful service history using SS with a coating of Blue Moly on the threads and under the heads on assembly.
     
    Last edited: Jun 24, 2023
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  5. abosely
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    abosely Senior Member

    Yes would be for durable color. But guessing coating SS used in saltwater environment wouldn’t be wise because of crevice pitting because coating would seal SS from oxygen.

    Wanted to verify that completely coating SS would wouldn’t be wise to do.
     
  6. jehardiman
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    jehardiman Senior Member

    Only as wise as the first nick in the coating.
     
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  7. comfisherman
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    comfisherman Senior Member

    Above or below waterline? Ive baked a ton of cerakote since 2011, have only done minimal underwater coating.
     
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  8. abosely
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    abosely Senior Member

    Would be above waterline, but would get saltwater on it.

    It’s not a major issue if completely coating SS in Cerakote can cause problems, won’t do it.
    Was guessing it probability wouldn’t be wise because of crevice pitting, but thought I would ask.
     
  9. jehardiman
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    jehardiman Senior Member

    Above the waterline it should be ok, just like a good coal tar epoxy paint would be ok. However if is constantly connected to saltwater or wear...things could be different once holidays start opening up. It's not the cost, it's the upkeep.
     
  10. abosely
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    abosely Senior Member

    Sounds like probably better to leave SS bare and not create an additional maintenance & inspection job.

    Would just be for color, so not really that important to coat.
     

  11. comfisherman
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    comfisherman Senior Member

    I'm doubtful you'd see a lot of crevice corrosion with cerakoted above the waterline. Or at least in any stretch of time that's going to be a bother. I've used it above waterline and on other personal devices since 2011 and haven't seen any instance of increased corrosion of any kind. It does chip, that's its one fault (Well that and difficulty applying compared to other coatings). Mostly used it on mild steel.

    I've been to nic and toured the r&d department, they have some awesome test facilities. They are incredibly helpful when talking to customer support and have happily told me some of my ideas were bad and reccomeneded other solutions.
     
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