We generally perform pickling of stainless steel products to remove weld scorch, rust, and other rust that may have occurred during the process.
In this case, it was not weld burn or trivial rust, but to remove rust on the inner surface of the pipe that runs inside the steel plate, which was caused by use over time.
The photo above shows the inside of the pipe after the rust removal. The rust has been removed to a sufficient level.
According to the specifications of the order, the pipe is then subjected to “rust prevention treatment” by acid washing. The pipes are then disinfected before shipping.