In this monograph was studied the effect caused in the microstructure and corrosion resistance by the heat input generated in the welding process in high strength and low alloy steels, a review which some samples of HSLA steels were welded or failing that, a heat treatment was applied in those was done in order to perform microscopy, lineal polarization, electrochemical impedance spectroscopy and some others corrosion techniques to study the electrochemical behaviour of the samples. According to results that different author have achieved was concluded that the corrosion resistance of weld joints depend on microstructural heterogeneity product of heat input in the weld process, so in conclusion, the corrosive attacks are highly possible to be concentrated in microstructures which has no homogeneity in its phases, usually the HAZ is zone who present the most microstructural variation in comparison with others