My water heater is making popcorn sounds?

Is it normal for my water heater to be making this kind of sounds? The water heater is a "Alliance" kind and its approximately 22 years old. On the exterior of the water heater there is calcium & soap scum build -up around it. What do you suggest on what option should i do about the popcorn sound? Do you... show more Is it normal for my water heater to be making this kind of sounds?

The water heater is a "Alliance" kind and its approximately 22 years old. On the exterior of the water heater there is calcium & soap scum build -up around it.

What do you suggest on what option should i do about the popcorn sound?

Do you recommend a water heater replacement?
OR
Do you recommend for an expert to come by my apartment and try to repair it?

I am very confused!

Thank You for your best advice answer.

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