A Comprehensive Guide to Corrosion Resistant Metal Parts
Under certain circumstances, even the strongest metal parts can suffer from corrosion, which is the result of the metal’s reaction with its environment. Corrosion changes the surface of a metal part into metal oxides, hydroxides, or sulfides. bass machining creates strong, durable parts.
Any metal can suffer from some degree of corrosion, although some metals react differently in different environments. Importantly, however, corrosion can usually be prevented or minimized by taking certain steps. These steps include good product design, material selection, and the application of surface treatments. This guide describes five of the best ways to reduce corrosion in metal parts manufactured using technologies such as CNC machining.
1.What is corrosion?
Corrosion is a natural process in which environmental conditions transform a refined metal into an oxide, hydroxide, or sulfide form. In the engineering world, electrochemical oxidation of metals (reaction with oxidants such as oxygen or sulfates) is the most common and most concerning form of corrosion, and iron rusting falls into this category. Some metals corrode easily when exposed only to moisture in the air, while others only corrode when exposed to other, more corrosive substances. Corroded metal is often identified by its orange color and powdery texture.
2.Preventing Corrosion
Steps can be taken to prevent metal parts from corroding. Most of these steps are performed before and during manufacturing, but they can also reduce corrosion after the parts are used. Following these steps will not guarantee that your parts will have an unlimited lifespan, but it can reduce potential corrosion to a certain extent while helping to maintain the normal function and appearance of metal parts.
① Choose corrosion-resistant metals
No metal is indestructible, but if your parts will come into contact with moisture or corrosive substances, it makes sense to choose corrosion-resistant metals.
- Stainless steel: Stainless steel contains iron, which oxidizes and rusts. However, steel with a high chromium content (such as stainless steel 316) is not easy to rust because the chromium forms a protective layer of chromium oxide on the surface of the parts.
- Aluminum: Aluminum does not contain iron, so it will not rust. When the parts absorb moisture, a protective layer of aluminum oxide forms on their surface to prevent corrosion.
- Copper, bronze and brass: Red metals such as copper, bronze and brass have very low or no iron content and will not rust. Copper oxide has a green sheen, and although this may not be aesthetically pleasing, it can protect copper parts from corrosion.
② Design parts that minimize environmental damage
The material of a part affects its corrosion resistance, but so do its shape and texture. Therefore, engineers should consider whether certain design features promote or prevent corrosion when creating CAD designs. Features that could trap moisture or air should be avoided. Parts should not contain deep crevices that could accumulate moisture, and airflow should be promoted as much as possible. If a part absolutely must contain crevices, tunnels, or other weak points, at least make these areas easy to clean and maintain.
③ Apply anti-corrosion coating
Applying a coating to a metal surface prevents metal corrosion because air, moisture, and other corrosive substances cannot directly contact the metal unless the coating itself wears off. The coating can be reapplied after a period of time to maintain the condition of the part.
Paint and/or primer are simple and inexpensive ways to prevent corrosion, and may still be necessary for aesthetic reasons. Powder coating can also form a protective layer of plastic material (epoxy, nylon, etc.) on the metal surface. For some metals, it may be best to add hard chrome plating (affordable, good corrosion resistance) or black chrome plating (more expensive, excellent corrosion resistance).
④ Apply sacrificial coatings
Another way to make parts corrosion-resistant is to apply sacrificial coatings to the metal instead of protective coatings.
The purpose of sacrificial coatings is not to prevent corrosion completely, but to allow the coating to corrode instead of the underlying material of the part. For this reason, such coatings are called “sacrificial” materials. An example of a sacrificial material is zinc or magnesium on a stainless steel part. Steel completely coated with zinc is called galvanized steel, and galvanizing is an example of cathodic protection: the steel becomes the cathode of an electrochemical cell. However, sacrificial materials do not have to be applied in the form of a coating; in the marine industry, blocks of zinc and magnesium against the protected parts are sometimes used to achieve a similar effect.
⑤ Control the environment around the part
Post-manufacturing steps may be more difficult to implement than pre-manufacturing steps, but corrosion can still be reduced once the part is in service. In some cases, the amount of substances such as oxygen or chlorine in the surrounding environment can be controlled. Parts can also be protected from excessive moisture by adjusting the position of the part or introducing barriers.