Alternate immersion testing of coated sheet steel

Journal Article · Thu May 01 00:00:00 EDT 1986 · Corrosion (Houston); (United States)

DOI:https://doi.org/10.5006/1.3584901· OSTI ID:5163863

Jones, D A; Blitz, R K; Hodjati, I

Alternate immersion cyclic exposure of prime coated and scribed steel sheet resulted in a lifting of the coating at the edges of the scribe. A thick oxide corrosion product film grew in the scribe and under the adjacent coating. Continuous immersion did not produce thick oxide films or a lifting of the coating. A zinc phosphate pretreatment limited the growth of the oxide to an area within the scribe and prevented attack at the coating/metal interface during cyclic exposure. polarization resistance, which was measured during the immersion segment of the cycle, was greater for phosphate specimens, reflecting the lesser extent of corrosion at the scribe edges. However, sensitivity was not high enough to produce any advantage over simple visual examination and measurement. In the presence of thick oxide films in the scribe, potential changes were very slow, and a modified procedure was necessary for measuring polarization resistance. Galvanized and Zincrometal treated specimens were resistant to the lifting of the primer coat during cyclic exposure, and phosphate pretreatment had little effect. In these cases, polarization resistance measured the galvanic dissolution of zinc to some extent, and polarization resistance values were comparatively low. A mechanism is discussed to account for the aggressive nature of alternate immersion exposures.

• Research Organization: Dept. of Chemical and Metallurgical Engineering, Univ. of Nevada-Reno, Reno, NV 89557
• OSTI ID: 5163863
• Journal Information: Corrosion (Houston); (United States), Vol. 42:5
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
STEELS
CORROSION RESISTANCE
PROTECTIVE COATINGS
TESTING
ZINC PHOSPHATES
CORROSION PRODUCTS
CORROSION PROTECTION
DISSOLUTION
ELECTRIC CONDUCTIVITY
INSPECTION
OXIDES
POLARIZATION
ALLOYS
CHALCOGENIDES
COATINGS
ELECTRICAL PROPERTIES
IRON ALLOYS
IRON BASE ALLOYS
OXYGEN COMPOUNDS
PHOSPHATES
PHOSPHORUS COMPOUNDS
PHYSICAL PROPERTIES
ZINC COMPOUNDS
360105* - Metals & Alloys- Corrosion & Erosion