Orthophosphate　is　widely　used　to　control　lead　(Pb)　release　in　drinking　water　distribution　systems,　but　phosphorus　addition　is　not　sustainable.　Alternative　corrosion　control　treatments　are　needed,　and　sodium　silicate　is　one　possibility.　Here,　pre-corroded　Pb　coupons-with　and　without　free　chlorine-were　used　to　examine　early-phase　corrosion　scale　development　after　silicate　addition,　with　orthophosphate　as　a　reference　corrosion　inhibitor.　Scale　development　was　evaluated　in　terms　of　total　Pb　release,　phase　transformation,　electrochemical　impedance,　morphological　changes,　Pb　dissolution　kinetics,　and　short-term　Pb-Cu　galvanic　corrosion.　Elevated　Pb　release　occurred　for　approximately　one　month　after　silicate　addition,　and　total　Pb　release　peaked　at　1968.1　mu　g/L　and　1176.9　mu　g/L　from　systems　with　and　without　free　chlorine,　respectively.　In　contrast,　orthophosphate-treated　coupons　exhibited　fewer,　less　pronounced　spikes　in　Pb　release.　By　day　354,　the　median　total　Pb　release　from　orthophosphate-treated　coupons　with　and　without　free　chlorine　had　decreased　to　3.7　and　5.0　mu　g/L,　respectively,　while　the　median　total　Pb　release　from　corresponding　silicate-treated　coupons　was　much　higher,　at　44.9　mu　g/L　and　34.3　mu　g/L.　Calcium　lead　apatite　(Ca0.56Pb3.77(PO4)(3)OH0.67)　was　identified　in　orthophosphate-treated　scales,　with　hydroxylpyromorphite　(Pb-5(PO4)(3)OH)　present　in　the　absence　of　free　chlorine.　Plattnerite　occurred　on　coupons　in　all　chlorinated　systems.　Pb　silicate　compounds　were　not　detected,　but　Ca2SiO4　and　Na2Ca2(SiO3)(3)　were　identified　by　X-ray　powder　diffraction.　The　charge　transfer:　film　resistance　ratio　characterizing　the　orthophosphate-treated　coupons　decreased　slowly　while　that　of　the　silicate-treated　coupons　increased　after　silicate　was　added.　These　variations　suggest　orthophosphate　provided　better　corrosion　control　than　silicate　did.　Silicate　treatment　generally　caused　degradation　of　the　top　Pb　scale　layer,　resulting　in　elevated　Pb　release,　while　orthophosphate　encouraged　the　growth　of　more　structured,　generally　thicker,　corrosion　scales　that　were　effective　in　limiting　Pb　release.