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HARD – SOFT – HARD

PROTECTIVE COATINGS FOR PISTONS

Ivan Ksenofontov, Alexander Lebedev
Photo: by Alexandr Batyru
“MOTO”, 2002, No.3

 

The weak spot of an engine is pistons. Their quality and reliability are one big headache of every car mechanic. People owning motorcycles made in Russia (“sovok” goods) are casting covetous glances at imported vehicles. But at present the cause for envy exists no more: the medicine against engines’ mortal disease called wear is already found by specialists in tribology. They offered the method to minimize effect of friction available for everybody: to apply “slippery” score-preventive coatings on a friction pair. It remains only to select the most appropriate substance.

Achievements of the science of friction – tribology – allow driving back vicious wear of engine parts. Solid lubricants take up the struggle.
  
We have compared two solid piston lubricants: the new preparation MC-2000 developed by the Russian company VMPAUTO, Saint-Petersburg, and the special coating Molykote D-10 of the company Dow Corning, Germany.

Summoned to the ring are …

Molykote is a dry score-preventive coating, which “shields” friction surfaces by means of   graphitization of metal. The agent shall be applied by spraying to the degreased surface of the piston (skirt) heated to the temperature 30 to 40°C. The layer shall then be dried up during 2 hours at the temperature 160 – 180°C.

MC-2000 is a solid lubricant coating. It is a metal-polymeric agent containing molybdenum disulfide, which is recognized to be a good antifrictional additive. The procedure of treatment is identical to that of Molykote, but the agent shall be applied on the piston surface with a brush. To ensure stable coating and accelerate hardening of MC-2000, it will be enough to keep the piston in an ordinary bake oven at the temperature 120 – 150°C for 2 hours. It is possible to omit heating, but then drying will take 24 hours. 
It would be advisable to apply to the piston skirt one to three layers of slippery substances, with some time intervals between each treatment. At the room temperature the agent MC-2000 is drying for 30 min. Molykote coating requires treatment in an oven. Racing drivers and amateurs of going to extremes will need to apply on pistons of their motorcycles several layers of coating.

The appearance and all performance characteristics of both agents are identical. Both are black “as the night”, withstand high temperatures up to 380 – 450°C and retain their properties during the time interval exceeding the time of running-in of the engine. Promises of manufactures are very tempting for customers: applied coatings shall reduce friction in the sleeve assembly (therefore, reduce wear), ensure fault-free piston operation even in the case of overheating or deficit of lubricant and reduce fuel consumption.


 
Photo 1. Molykote coating is applied by means of a conventional sprayer. Piston rings and the bottom are covered by foil. The cost of the agent used to protect two pistons is 120 to 140 rubles.
 
Photo 2. The agent MC-2000 is applied on the surface with a brush. The cost of the agent used to protect two pistons is 70 to 80 rubles.



















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