The energetics of the step faceting transition of Cu(001) [copper (001) surface] upon Cl (chloride) adsorption in contact with HCl (hydrogen chloride) solution is modeled in terms of a solid-on-solid model that incorporates both nearest-neighbor and next-nearest-neighbor interactions. It is shown that faceting of the closed packed  Cu(001) steps into step segments oriented along  directions of the Cu(001)-c(2×2)Cl can be explained by a strongly repulsive interaction between next-nearest-neighbor Cl atoms in the c(2×2) adlayer. The dynamics of kink motion along the -oriented steps of the Cl-covered Cu(001) surface via attachment/detachment is studied with scanning tunneling microscopy. At some kink sites local dissolution takes place, whereas at other kink sites growth occurs. After correcting for the net local dissolution (or growth) process the kinks perform a one-dimensional random walk along the  oriented step segments.