The Effect of Sodium Chloride Particles on the Atmospheric Corrosion of Pure Copper

• The atmospheric corrosion of copper has been investigated after deposition of sodium chloride (NaCl) particles and 10 days of subsequent exposure to clean, humidified air below, near, and above the point of deliquescence of NaCl (at around 75% relative humidity (RH), Microgravimetry, Fourier transform infrared (FTIR) microspectroscopy, scanning electron microscopy with x-ray microanalysis, and scanning Kelvin probe were used to identify corrosion processes and products. The NaCl deposition resulted in the evenly distributed NaCl particle clusters with a diameter of approximately 100 μm. The clusters consisted of individual NaCl particles of <10 μm. The mass gain increased linearly with the amount of NaCl particles added in the range of this study (up to 4 μg/cm2). Even at very low RH (55%), which lies far below the point of deliquescence (75%), copper with NaCl particles added suffered from significant corrosion attack and the mass gain of copper with 4 μg/cm2 NaCl added was about 7 μg/cm2 after 10 days of exposure. At 55% RH, the NaCl particles did not dissolve. However, significant chloride-induced corrosion effects were observed after 10 days, both in the original particle cluster and in a 20-μm-wide outer zone into which chloride ions had dffused radially. At 75% RH, the NaCl particles dissolved and chloride ions diffused to cover the whole surface. Chloride-accelerated corrosion effects resulted in the formation of cuprite (Cu2O) and copper carbonate, mainly in the area of the original particle cluster. The corrosion effects accelerated further at 95% PH, resulting in the formation of Cu2O over the whole surface and copper carbonate in a concentric zone outside the original particle cluster. The distribution of the corrosion products was related to the localization of the anodic and cathodic reactions during the corrosion process.

Ämnesord

NATURVETENSKAP  -- Kemi -- Materialkemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Materials Chemistry (hsv//eng)

Nyckelord

Atmospheric corrosion

Copper

Deliquescence

Humidity

Sodium chloride particles

Materials chemistry

Materialkemi

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