Masoud ASTM A 490 bolts are quenched and tempered hexagonal structural medium alloy steel bolts with high 150 KSI tensile strength. Hot dip galvanizing, metal deposition, electroplating with zinc should not be done. If you wish to protect these high strength bolts from thread corrosion or from likely fire retardant purposes or in places with high rainfall or with prevailing atmospheric corrosive environment + also from fire retardant purposes, you could apply molybdenum coating (Moly-coat) powder available in market. Moly coat is applied to protect threads from corrosion and also ease from preventing rusting / corrosion in such high tensile bolts in many industries for these purposes. Hope this helps C.V.Srinivasan Nishi Engineers Pvt Ltd India August 7, 2010 E-mail: nishi@vsnl.com >Is it permissible to hot galvanize bolts of type A490? > Referring to some standards acid pickling in hot >galvanizing process has the risk of hydrogen embrittlment. >Is it possible to use mechanical cleaning instead of acid >pickling? >What type of coating you recommend instead of hot >galvanizing? >Regards, >masoud