The effects of the surrounding humidity on the friction and wear properties of electroless Ni-P alloy coating on iron substrate against various steel balls were evaluated by using a horizontal reciprocating friction and wear test apparatus. The friction and wear properties greatly changed due to the surrounding humidity in spite of being under equal friction and wear testing conditions. The friction coefficient and wear amount decreased with the increase in the surrounding humidity. Therefore, it was proven that the water which adsorbs to the specimen's surface showed the lubricating effect.
