Paints and varnishes. Filiform corrosion test on steel

1986 ◽  
Keyword(s):  
Corrosion Test ◽  
Filiform Corrosion

Study of factors affecting corrosion of aluminum automotive wheels

1993 ◽  
Vol 51 ◽  
pp. 1182-1183
Author(s):  
H. K. Plummer ◽  
R. N. Simmons ◽  
R. W. Ocobock ◽  
T. A. Honey ◽  
M. C. Paputa Peck
Keyword(s):  
Corrosion Test ◽  
Uv Exposure ◽  
Uv Absorbance ◽  
Water Spray ◽  
Surface Layers ◽  
Accelerated Corrosion ◽  
Factors Affecting ◽  
Accelerated Corrosion Testing ◽  
Filiform Corrosion ◽  
Accelerated Corrosion Test

Aluminum automotive wheels, which have been used since the mid 1970’s, have proven to be very rugged, but early wheels discolored with time. Since 1976 the machined “bright” exterior surfaces, have been coated with a chromium based “conversion” pretreatment, and painted with a “clearcoat” of polyester or acrylic to preserve appearance. These coated wheels can exhibit “filiform” corrosion between the Al surface and the clearcoat (Fig. 1). The corrosion is filamentous and closely follows aluminum grain boundaries. Corrosion results from oxidation of the aluminum (anode) in the presence of water and oxygen at a break (cathode) which intrudes through the clearcoat and conversion coat into the aluminum (Fig. 2). Current specifications require ≤ 1.6 mm filiform corrosion from a scratch after 400 h of accelerated corrosion testing. This paper correlates accelerated corrosion with the composition of the clearcoat paint, the UV absorbance of the paint and the microstructure of the Al / Cr conversion coat / clearcoat interface to learn the necessary parameters to produce Al wheels with enhanced protection. Production Al wheels, from a variety of sources, wheels prepared to our specifications and a design of experiments (DOE) wheel series prepared in our laboratories were examined.The accelerated corrosion test exposes the test piece to UV weathering (400 h) with four water spray cycles every 23 h. After UV exposure the surface is scratched through the surface layers into the Al metal with a carbide scribe, followed by exposure to HCl vapor (1 h).

scholarly journals Effects of Alloying Elements on the Corrosion Behavior of Sputter–deposited Zr–(12–21)Cr–W Alloys in 0.5 M NaCl Solution

1970 ◽  
Vol 25 ◽  
pp. 75-82
Author(s):  
Basu Ram Aryal ◽  
Jagadeesh Bhattarai
Keyword(s):  
Corrosion Test ◽  
Open Circuit Potential ◽  
Chemical Society ◽  
Open Circuit ◽  
Sputter Deposition ◽  
Nacl Solution ◽  
Corrosion Rates ◽  
Sputter Deposited ◽  
Stable Passivity ◽  
Zirconium Metal

The synergistic effect of the simultaneous additions of tungsten and zirconium in thesputter-deposited amorphous or nanocrystalline Zr-(12-21)Cr-W alloys is studied in 0.5 MNaCl solution open to air at 25°C using corrosion tests and open circuit potentialmeasurements. Corrosion rates of the sputter-deposited Zr-(12-21)Cr-W alloys containing10-80 at % tungsten (that is, 0.95-1.85 x 10-2 mm.y-1) are more than one order of magnitudelower than that of the sputter-deposited tungsten and even lower than those of zirconium aswell as chromium in 0.5 M NaCl solution. The addition of 8-73 at % zirconium content inthe sputter-deposited binary W-(12-21)Cr alloys seems to be more effective to improve thecorrosion-resistant properties of the sputter-deposited ternary Zr-Cr-W alloys containing12-21 at % chromium in 0.5 M NaCl solution. The sputter-deposited Zr-(17-21)Cr-W alloyscontaining an adequate amounts of zirconium metal showed the more stable passivity andshowed higher corrosion resistance than those of alloy-constituting elements in 0.5 M NaClsolution open to air at 25°C.Keywords: Zr-(12-21)Cr-W alloys, sputter deposition, corrosion test, open circuit potential,0.5 M NaCl.DOI:  10.3126/jncs.v25i0.3305Journal of Nepal Chemical Society Volume 25, 2010 pp 75-82

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