Prevention of corrosion is of prime importance. It not only saves money but also helps in preventing accidents such as a bridge collapse of failure of a key component due to corrosion. Statue of liberty is easily identified by it’s height, stance and unique blue-green colour. When this statue was first delivered from France, its appearance was not green. It was brown. The change in appearance was a direct result of corrosion. Which of the following is/are useful to prevent corrosion