Need help making a high temp pigment

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Discussion Overview

The discussion revolves around the challenge of developing a high-temperature pigment suitable for use in engineering applications, specifically for products operating at temperatures exceeding 1000°C. Participants explore potential materials and methods to achieve a stable black dye that can withstand these conditions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests using graphite as a base for the pigment but raises concerns about the acidic pH of the current solution, proposing an alkaline wash to adjust the pH to the desired range of 8-8.5.
  • Another participant inquires about the base material and the previous dye used, seeking clarification on the specifics of the application.
  • A later reply specifies that the pigment will be applied to refractory bricks and/or stainless steel, noting that the previous dye, Shepherd 10K927, works well up to ~1200°C but has limitations.
  • One participant points out that graphite may oxidize at high temperatures in the presence of oxygen, potentially complicating its use as a pigment.
  • Another participant mentions Iron II Oxide as a stable black coating for steel fasteners, highlighting its high-temperature stability but also noting the risk of red rust if exposed to moisture.
  • The original poster expresses gratitude for the suggestions and indicates plans to test some prospective solutions soon.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best approach or material for the high-temperature pigment, with multiple competing views and suggestions remaining in the discussion.

Contextual Notes

There are unresolved questions regarding the specific interactions of the proposed materials at high temperatures, the effectiveness of the alkaline wash, and the implications of using graphite in oxidizing environments.

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I'll spare y'all the details but, in short, instead of previous plans I'd had, I've ended up doing exciting engineering work for a company in Virginia. Our products operate in very high-temperature environments (>1000C) routinely and we like to dye them black for visual appeal. As we look towards higher temp applications, our current dye will be insufficient. I'm looking to utilize graphite as the base of our pigment but, the pH is too acidic (~5, needs to be closer to 8-8.5). I'm an engineer, and not the colloidal chemistry kind. Would a simple alkaline wash be sufficient to maintain the desired pH? If I were to mix with an inert base material so that the average pH were in that 8-8.5 range, would that achieve the sort of results we're looking for? I apologize for the likely amateur questions but, I forgot all of ORGO the moment I finished the final exam.

Thanks in advance for any help y'all can provide!
 
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What is the base material ?
What was the previous dye ?
 
Baluncore said:
What is the base material ?
What was the previous dye ?
It'll be sprayed on refractory bricks and/or stainless steel. Previous dye was Shepherd 10K927 (pH 8.2) and it works well but, is limited to ~1200C. We've attempted Shepherd Black 444 (pH 6., slightly larger particle size) but, it caused everything to fall out of solution.
 
Graphite is an inert material at standard temperatures, but in the presence of oxygen, when the temperature reaches approximately 1000°C, the graphite will rapidly oxidise to CO or CO2.

Black 444 is used in applications where the absence of chromium is needed. Stainless steel contains at least 11% Cr, so you could use a Cr based pigment, or chemically convert the Cr surface of the stainless steel to a stable black compound.
 
Iron II Oxide. It is the black coating that you find on steel fasteners. Very stable at high temperatures. Can turn into red rust if you let it get wet. But the high temps will roast it back to black.
 
Would like to thank you all for your pointers! I've got a couple of prospectives going into testing on Monday. Fingers crossed but, I'm hopeful.
 
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