Page 485 - Corrosion Engineering Principles and Practice

452 C h a p t e r 1 1 M a t e r i a l s S e l e c t i o n , Te s t i n g , a n d D e s i g n C o n s i d e r a t i o n s 453

Plant Construction:
Prevailing wind direction OK?
Method of using cooling water defined (open recirculated, salt water, double
exchange, ponds, air cooling)?
Cooling tower downwind?
Closed construction used (pipe or box stanchions, etc.)?
Exterior designs free of pockets?
Tank bottoms protected (cathodically or sealed, depending on type)?
Metal-to-metal contacts protected?
Equipment designed properly for coating?
Will hydrotesting corrode the steel or leave chlorides on stainless steels?
Is a system of material verification needed?
Will all steel be cleaned and primed before erection?
Are temporary preservatives needed for some items?
Should cathodic protection be installed now?
Is electrical equipment properly grounded to prevent stray currents?
Equipment Design:
No ‘dead’ spaces in lines, tanks, vessels?
All possible crevices sealed or flushed?
Inlets-outlets properly contoured? (If not, is protection provided?)
Offsets on mechanical equipment properly filleted?
Other potential fatigue sites?
Can equipment be cleaned adequately if needed?
Will end grain attack be a problem?
Homogenizing anneal needed?
Stress relief required to forestall SCC?
Are weld deposits compatible with parent metal in chemistry and hardness?
Corrosion allowances added to metal thickness?
Possibility of liquid metal embrittlement (e.g., zinc on stainless)?
Desiccating vents needed?
Temperature:
Evaporation area-vaporization or ebullition cause problem?
Hot spots-from stream injection point?
Hot spots-due to impinging flame?
Cold spots-due to attachment of external metal?
Cold spots-condensation zone a problem? (If so, keep + 10°C above dew point.)

TABLE 11.3 Some Design Considerations to Control Corrosion