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Re: high temp powder coating tempered aluminum - don't do it
The above paper agrees with my experiences and some of my customers experiences we had with high temperature power coatings on aluminum parts over 30 years ago. I published my findings on s few other forums 10 to 15 years ago. After a few weeks many of the enthusiast on those forums talked to their local powder coating shops and the P C shops said I did not know what I was talking about. I then talked to a hand full of powder coating shops in the Phoenix Arizona area about the curing time and temperatures they used on their powders and the answers varied from 450 deg F for 15 minutes to 350 deg overnight. They also said that powder coating will not change the temper or age hardening of the aluminum. A powder coating shop owner, a quarter mile down the street from my shop, was put in the hospital by two bikers. I bought his fork lift when he closed his shop a few months after the hospital incident. The P C shop owner said that the bikers claimed they started blowing head gaskets and the valve seats would not stay pressed in the head. The bikers claimed their heads were ruined when they were powder coated and wanted the shop owner to buy them new heads. The PC shop owner told them that the 400 deg curing temp would not hurt their aluminum heads and he was not going to buy them new heads. Then the P C shop owner woke up in the hospital. When I was paying him for the fork lift he ask me what I thought about the bikers claims. I told him I stopped powder coating aluminum aluminum engine parts over 25 years ago because the curing process usually softened the aluminum and reduced the aluminum's ability to get rid of heat through two of the three forms objects can transfer heat to the atmosphere. The three forms objects can transfer heat are: conduction, convection and radiation. Any paint is an insulator and powder coating is an insulator on steroids which drastically reduces heat loss through convection and radiation. Air cooled engines are cooled primarily by convective heat transfer as air travels between the fins and a small amount of radiation off of the non finned areas. Polishing or chroming any surface reduces the amount of radiated heat loss. smooth surfaces reduce convective heat loss. This is another example I have observed or personally experienced where the powder coating curing process overaged the aluminum making it soft promoting head gasket sealing problems, relaxed the press fit on the valve seats and the reduced the convective heat loss through the fins, and elevated the head temperature to the point thermal expansion of the aluminum further reducing the press fit on the valves seats or valve guides to the point they would no longer stay in position. Have you ever seen a polished, powder coated, anodized or chromed plated engine, head or exhaust system on a "factory works bike"? I have not and I have worked on a lot of them. There are a lot of square inches of external surface area on engine cases and cylinders of liquid cooled engines that can be used to radiate heat and transfer heat to the atmosphere by convection as air flows over these areas. Using the proper surface preparation on ALL of these external engine surfaces reduces the amount of heat the radiator has to get rid of. I see a lot of customers fall victim to the inline aluminum finned cooling gadgets that produce turbulence and restriction inside any coolant line where they are installed. Anodizing also reduces radiated heat loss. One of the basic laws of physics says that metals that conduct heat well conduct electricity well. Metals that do not conduct heat well do not conduct electricity well. Check an anodized surface with an ohm meter and see what you get. I am attempting to educate the guys that are racers where performance is the primary goal. I am attempting to educate the guys who want to have a beautiful bike and what some of the bling may be costing them in performance and longevity. The laws of physics does not allow a true race bike and a museum queen to exist in one package! May 29, 2023, 12:15:51 AM |
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Re: “250R” get together (Little Sahara, Oklahoma) 2023
So cool September 29, 2023, 07:32:17 PM |
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Re: Three Wheeler Meetup 2024 Florence, Oregon
This weekend June 04, 2024, 07:43:49 PM |
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Re: Boss racing engine cases
Ready for purchase October 25, 2024, 07:37:34 PM |
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Re: Race pic (random) Atc250r
Salem indoor speedway. Salem,Oregon March 27, 2025, 07:06:17 AM |
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Re: trash or treasure ?
Sand the area with a 150 to 200 grit cartridge roll until you can't see the blemish/crack. Put the case into the oven and heat the case up to about 200 deg. F. If there is a crack, oil in the crack will expand and the crack will become visible.
April 10, 2025, 09:25:27 PM |
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Re: Cool Pics/Videos Thread
Honda MVX250F May 26, 2025, 01:38:51 PM |
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