Summary for non conductive high temp coating Discussion
Non conductive high temp coating is the core challenge here: the question asks for a coating on 316 stainless steel that can provide electrical insulation at 24 volts/1 amp, survive continuous 300 °C service, resist abrasion, corrosion, chemicals, and steam pressure, and still offer a non-stick surface. The asker reports that PTFE (Teflon) failed on abrasion, temperature, thickness, and insulation, while aluminum-oxide ceramic had the temperature and wear resistance but not electrical insulation. James Watts says the requirement is unusually demanding and warns that most plastics expand far more than 316 stainless and will soften or melt at 300 °C. He suggests trying a Teflon sleeve, noting that different Teflons and applicators exist and that a thicker or multi-coat approach may help. He also asks whether a Pyrex glass tube with Teflon O-rings on the ends could work, implying the application may need a different design rather than a single coating.
Q. WE ARE IN SEARCH OF COATING WHICH HAS
[1] ELECTRICAL INSULATION – 24 VOLTS AND 1 AMP. CURRENT[2] RESISTANCE AND CAN WITHSTAND CONTINUOUS HIGH TEMPERATURE MAX. UP TO 300* CENTIGRADE
[3] COATING SHOULD BE ABRASION RESISTANT, CORROSION AND CHEMICAL RESISTANT, HAS A NON STICK SURFACE
THE PART TO BE COATED IS OF STAINLESS STEEL MATERIAL 316, SIZE 6.4 MM O.D. AND 400 MM LONG.IT IS SUBJECT TO THE CONTINUOUS TEMPERATURE OF 300 °C AND STEAM PRESSURE OF 895 PSI.
WE HAVE TRIED TEFLON COATING BUT IT IS NOT ABRASION RESISTANT, CAN NOT BEAR CONTINUOUS THE TEMP. OF 300 °C AND COATING THICKNESS IS VERY THIN HENCE IT LOOSE ITS ELECTRICAL INSULATION PROPERTY.
THE CERAMIC COATING WITH ALUMINUM OXIDE HAS TEMP. RATING AND ABRASION RESISTANCE BUT HAS NOT ELECTRICAL INSULATION PROPERTY.
CAN ANY ONE SUGGEST THE COATING FOR THIS APPLICATION
MILESH VORA
– SURENDRANAGAR, GUJARAT, INDIA
A. Your requirement is unusually demanding. Consider that most plastics have a coefficient of expansion about 10 times greater than the 316 is a problem. Also, most plastics will become rather soft at that temp, if not melted.
Options to try might be a teflon sleeve. Depending on your use, this may not work.
There are many teflons and many applicators. Look for a better teflon for your needs and one that can either be put on thicker or in multiple coats.
Is a pyrex glass tube with teflon O-rings on the ends an option.
James Watts
– Navarre, Florida
2005
 | A. Glass cloth works. It can be obtained (at least in the USA) as a cloth, woven into an expandable tube, as tape with or without adhesive, and non-woven as glass fiber. Tom Gallant A. Ceramics are not conductive and very good insulators indeed. I don’t understand why your aluminum oxide coating didn’t work under such a low voltage. You should review how it was applied, its purity, thickness, porosity, etc. Then, look for a way to improve it. Most surely you will end up selecting one of the numerous ceramic coating systems for your application. Guillermo Marrufo |
A. Additional information about the dielectric properties of aluminum oxide (according to www.accuratus.com). It has a dielectric strength of 418 volts/mil or 16.7 kv/mm. I don’t know the thickness of your failed alumina coating but maybe is a matter of increasing it.
Guillermo Marrufo
Monterrey, NL, Mexico
2005
A. STEELPAK 86Cr IS BEST COATING FOR YOUR APPLICATION. IT HAS BOTH HIGH WEAR RESISTANCE AND ELECTRICAL INSULATING PROPERTIES.
KRISHNA MOORTHY S
– Bangalore, Karnataka, India
October 8, 2016