Research On Technology Of Hot Dipped Galfan Coating Of Sucker Rods And Its Properties

Sucker rod corrosion will seriously affect the oilfield normal production,the cost of hot dipping Galfan alloy is low,and can effectively improve heat resistance and corrosion resistance performance of plating,its coating corrosion performance is better and improve 1² times than other hot dipping Zn-Al coating.But the current production and research is limitated on the steel wire,oil pipe.At the base of using hardened and tempered 35CrMo sucker rod as steel base,adopting solvent method to hot dipping Galfan alloy in this topic,covering agent formula was designed,optimized,and validated.The influence of single or double dipping process and their parameters on coating quality were laso analyzed.At the same time the formation mechanism of Galfan alloy plating was also analyzed.The influence of adding Al content changes on the performance of the anticorrosive coating was also analyzed.The corrosion processes of Galfan alloy coating layer in the artificial corrosion medium was observed and analyzed.Also discuss the anticorrosion mechanism.It is indicated that:Determine the optimum temperature range of hot dip Galfan is 430⁴50℃and the dipping time is 90s.Single and double dipping coating are both two layers,the outer layer is the Galfan alloy layer,and the inner layer which is close to base is intermediate transition layer.The thickness of the double dipping coating is larger than the single one.Aluminum content in the intermediate transition layer of internal coating position which is close to iron-based exsist peak in both two kinds of coating.Iron content in transition layer of single coating decreased sharply while it gradually reduce from steel base to the outside of the coating in double dipping coating.Zinc content increased sharply in intermediate transition layer of single dipping coating while it it gradually reduce from steel base to the outside of the coating in double dipping coating.In the position of Galfan alloy coating which is near the steel base it is FeAl Znx and near the outer layer region it is FeAl₃Znx.Double coating were better than the single coating in hardness,corrosion resistance and mechanical properties.With the Aluminum heavily involved reaction,the stability of the Galfan alloy liquid component was destroyed,which leads to the formation of pure zinc grains on the surface of the coating.The influence of different amount of Al content on coating corrosion resistance is not the same.When the adding amount Al is 5%,the microstructure is dense eutectic state,intermediate layer is very thin,the quality and corrosion resistance of coating are the best.The corrosion direction of the Galfan coating is extended from the intergranular to the eutectic structure,and corrosion gradually turn put to be well-distributed.The corrosion developed from the coating surface to the iron matrix in the direction perpendicular to the coating surface.