Need help making a high temp pigment

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SUMMARY

The discussion focuses on developing a high-temperature pigment for products operating above 1000°C. The engineer is exploring the use of graphite as a base pigment but faces challenges with pH levels, currently at 5, which need to be adjusted to between 8 and 8.5. Previous dyes, such as Shepherd 10K927 and Shepherd Black 444, have limitations in temperature resistance and solubility. Suggestions include using an alkaline wash and considering Iron II Oxide for its stability at high temperatures.

PREREQUISITES
  • Understanding of colloidal chemistry principles
  • Knowledge of high-temperature material properties
  • Familiarity with pigment formulation and pH adjustment techniques
  • Experience with refractory materials and their applications
NEXT STEPS
  • Research methods for adjusting pH in pigment formulations
  • Investigate the properties and applications of Iron II Oxide as a pigment
  • Explore the effects of high temperatures on graphite and its oxidation
  • Learn about alternative high-temperature dyes and their chemical stability
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Engineers, material scientists, and product developers working with high-temperature applications, particularly those involved in pigment formulation and surface coatings for refractory materials and stainless steel.

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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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