Damage caused by anti-corrosion coating electrodes
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If two materials with different potential differences are present in the coating layer, galvanic corrosion can cause damage to the coating layer. If an oil storage tank is treated anti-statically by aluminum spraying followed by sealing with a coating containing carbon black or graphite powder, this will cause aluminum to act as an anode, accelerating corrosion and leading to the peeling and damage of the coating layer. Another example is food cans or containers made of tinplate coated with an organic varnish; when defects in the tin coating expose the iron, in an acidic food electrolyte, tin acts as the cathode while iron serves as the anode, resulting in galvanic corrosion that causes the coating to peel off.
When a coating contains materials with two different potentials, galvanic corrosion is likely to occur, leading to damage to the coating. For example, to prevent static electricity in oil storage tanks, they are first coated with aluminum, and then the pores are sealed with a coating containing carbon black or graphite. As a result, aluminum became the anode, accelerating corrosion and ultimately causing the coating to peel off. Another example is food cans made of tinplate, which have their surface coated with tin and then painted. If the tin coating is damaged and iron is exposed, in acidic foods, tin acts as the cathode while iron acts as the anode, leading to galvanic corrosion that causes the coating to peel off. .