Page 283 - Challenges in Corrosion Costs Causes Consequences and Control(2015)

CORROSION CONTROL OF STORAGE TANKS 261

TABLE 4.27 Corrosion Control Methods for Aboveground Storage Tanks
Corrosion Mode Control Method
Uniform corrosion Inhibitors; protective coating; cathodic protection
Intergranular Avoiding temperatures that cause contaminant precipitation during
corrosion heat treatment or welding
Pitting corrosion Protective coating; allowance for corrosion in wall thickness
Stress corrosion Reducing residual or applied stress; redistributing stresses; avoiding
misalignment of sections joined by bolts, rivets, or welds; using
materials of similar expansion coefficients in one structure;
protective coating; cathodic protection.
Corrosion fatigue Minimizing cyclic stresses and vibrations; reinforcing critical areas;
redistributing stresses; avoiding rapid changes in load, temperature,
or pressure. Inducing compressive stresses through peening,
swagging, rolling, vapor blasting, chain tumbling
Galvanic corrosion Avoiding galvanic couples; completely insulating dissimilar metals;
using filer rods of same chemical composition as metal surface
during welding; avoiding unfavorable area relationships; using
favorable area relationships; cathodic protection; inhibitors
Thermogalvanic Avoiding nonuniform heating and cooling; maintaining uniform
corrosion coating or insulation thickness
Crevice corrosion Avoiding sharp corners and stagnant areas; minimizing crevices in
concentration heat transfer areas and in aqueous media containing dissolved
cells oxygen or inorganic solutions; enveloping or sealing crevices;
protective coating; removing dirt and mill scale during clearing
surface
Erosion Decreasing flow velocity to laminar flow; minimizing abrupt changes
impingement in flow direction; streamline flowing; installing replaceable
attack impingement plates at critical points in flow line; using filters and
steam traps to remove solids and steam protective coatings;
cathodic protection
Cavitation damage Maintaining pressure above liquid vapor pressure; minimizing
hydrodynamic pressure differences; protective coating; cathodic
protection; injecting or generating larger bubbles
Fretting corrosion Installing barriers that allow for slip between metals; increasing load
to stop motion, but not above load capacity; porous protective
coating; lubricant
Hydrogen Low-hydrogen welding electrodes; avoiding incorrect pickling,
embrittlement surface preparation, and treatment methods; inducing compressive
∘
stresses; baking metal at 93–148 C to remove hydrogen;
impervious coating such as rubber or plastic
Stray-current Providing good lubrication on electric cables and components;
corrosion grounding exposed components or electrical equipment; draining
off stray currents with another conductor; electrically bonding
metallic structures; cathodic protection
Different Protective coating; cathodic protection; avoiding partially buried
environment structures; underlaying and backfilling underground pipelines and
cells tanks with the same material