Passivation Twice??

//Passivation Twice??
Passivation Twice??2018-06-05T02:27:39+00:00

Home Forums Fastener Production Passivation Twice??

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  • Jesse Mawson
    Participant
    Post count: 5

    My customer is inquiring about a SS deck screw, and he asks this:
    Is it possible to manufacture this screw geometry in US 410 (hardened stainless steel) incl. surface 2x passivated?

    He is telling me that their current Taiwanese supplier passivates the screws once before heat treatment and again after heat treatment. I have never heard of passivation done twice on the same screw. Is this really necessary? My understanding is that passivation forms a protective layer and is done in the last step of production. Any advice?

    Bojen Chen
    Participant
    Post count: 9

    I think there is no point passivating the screws before heat treatment.

    Jesse Mawson
    Participant
    Post count: 5

    Explanations of customer:

    because the corrosion protection is increased, therefore 2x.

    Another reason for this may be that there is no rust between the production process and the hardening process when the screws are stored for several days in between.

    not sure if I should believe him, seems redundant to passivate twice

    Vishaan Zaydin
    Participant
    Post count: 4

    A2 is passivated once, but SS 410 is passivated twice; your customer is correct about this.

    The reason SS 410 is passivated twice is because before the heat treatment the oil must be removed from the surface; the oil stain becomes very difficult to remove after the heat treatment.

    The second time these screw are passivated is to produce the protective layer on screws.

    John Brooks
    Participant
    Post count: 10

    Passivation is done twice mostly for self drilling screws (using heat treated 410 for hardness), since for A2 you do not heat treatment them and therefore passivation is only done once as the final production step.

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