12.8 Corrosion Control Flashcards
what is the maximum contaminant level goal for lead?
zero
why is the MCLG zero for lead?
adverse effects to nervous system and growth and development of children
is the copper action level health based? is the lead action level health based?
yes, no
is exceeding the action level for lead a violation under the LCR?
no
what is the cause of corrosion in pipes?
low pH
default tool to determine the stability of treated water
Langelier Saturation Index
when water contacts metal surface, elemental lead at the surface will _________ (oxidize) to Pb(II) or Pb(IV) which leads to a lead mineral ______ on the surface
corrode, scale
in the presence of chloramine or free chlorine residual, elemental lead will oxidize to Pb(II) and at a typical pH will in turn form lead ____________
carbonate
what are the three oxidation states of lead?
Pb(0), Pb(II), Pb(IV)
two common corrosion inhibitors
orthophosphate and silicaye
the most successful strategy for chemical inhibitors are the elevation of _______ and addition of _______
pH, orthophosphate
evaluates the potential for corrosion of cast-iron pipes transporting water from the Great Lakes
Larson-Skid index
the Larson-Skid index determines the effect of c_______, s_____ and bicarbonate/carbonate ions on the corrosivity of treated water toward iron pipes
chloride, sulfate
A Larson-Skid index of less than 0.8 suggests that chloride and sulfate levels are not likely to cause c_________
corrosion
