In-situ atomic force microscopy has been used to investigate the dissolution behavior of industrially relevant silicoaluminophosphate catalysts SAPO-34 and SAPO-18. Spiral growth is prevalent on these materials and it is common for the spirals to be composites of multiple dislocation sources. The spirals dissolve via classical step retreat and the structure dissolves in a two-step process via unstable intermediates. The data support the proposition that the terminating surface of SAPO-34 is composed of double 6-rings. SAPO-34 and SAPO-18 both dissolve by removal of the same structural units with similar mechanisms.