Experimental measurement of general attack corrosion is usually made by measuring ________________ and calculating ________________.

• A. Weight loss, the equivalent loss of metal thickness.
• B. Color change and surface roughness.
• C. Electrical resistance and current density.
• D. Mass gain and volume increase.

Answer: (A)

General (uniform) attack corrosion removes metal evenly from the surface, so the most straightforward way to quantify it is by measuring how much metal is lost. You weigh the specimen before and after exposure; the difference is the weight loss. To compare different samples or convert to a more universal metric, turn that weight loss into an equivalent thickness of metal removed: thickness loss = weight loss / (area × density). This gives a representative metal-thickness loss (in mm) that, divided by the exposure time, yields a corrosion rate.

Color change and surface roughness are qualitative indicators and don’t quantify material loss. Electrical resistance and current density relate to electrochemical activity but don’t directly measure uniform metal loss for general attack. Mass gain or volume increase would indicate oxide growth or deposits, not the typical metal loss from general attack.