Do All Rust Removers Contain Phosphoric Acid?
It’s a common practice to package rust treatment products containing phosphoric acid and improperly label them as a “rust remover”. But the phosphoric acid in these products actually works as a rust converter, which is an altogether different and distinct group of rust treatment product.
Acid-based rust removal products normally contain an acid or caustic solution such as oxalic acid as an active ingredient to strip the rust from the metal surface. Unfortunately, oxalic acid is a harsh and toxic chemical which could pose a health risk to anyone who gets into contact with it.
Homemade rust removers such as lemon or lime juice and white vinegar also work on the same principle. Lemon and lime both contain citric acid while vinegar is a diluted solution of acetic acid.
As a homemade rust remover, the acetic acid found in white vinegar works by reacting with rust to form a harmless, soluble salt that you can simply washed away. Although homemade rust removers are not as effective as oxalic acid in treating heavily corroded metal objects.
On the other hand, rust removal products containing phosphoric acid as an active ingredient should be classified as “rust converters”. They’re only promoted as rust removers to generate more sales at the hardware since consumers are more familiar with the latter category.
Rust converters do not remove or strip away rust. Instead, the phosphoric acid works on the rust (iron oxide) with a reddish brown hue into a harmless, blackish compound known as iron phosphate.
Curiously enough, iron phosphate provides additional protection to a metal surface by preventing any more corrosion from taking place. Moreover, you can extend the life of the iron phosphate covering by adding a rust-resistant topcoat over it.
Rust converters are actually the rust treatment product of first choice by the DIY homeowner. Compared to rust removers, phosphoric acid-based rust converters are inexpensive, easy to apply, and safe to use. In short, you get more work done with the least amount of effort and expense.
You may be surprised to learn that you could already have a sizeable stock of rust converters in your fridge. It’s rich in phosphoric and carbonic acid and, most probably, you and your family drink a lot of it on a daily basis. As a matter of fact, it’s the most consumed beverage in the world today. It’s none other than soda.
So if you need to treat a small metal objects laden with rust but you don’t have time to go to the hardware, you can simply immerse them on a glass of Coke overnight. The next morning, you’ll be surprised to discover that the corrosion is gone. That’s phosphoric acid in action!