True to its name, stainless steel (SS) is loaded with high corrosion-resisting properties and (almost) everyone knows that. What everyone doesn’t know is that stainless steel products are subject to surface damage if not cleaned properly. Corrosion, rusting, oxidation, or staining can occur as a result of prolonged exposure to harsh environments.
The SS corrosion resistance properties are enhanced by raising the chromium content. Additionally, other elements like molybdenum, nitrogen, and nickel are also added to keep corrosion at bay. This, in turn, adds up to stainless steel prices.
Stainless steel comprises a minimum 10.5% chromium. The chromium content creates a protective shield known as the passive layer. This, in turn, safeguards stainless steel from corrosion. The higher the proportion of chromium content is, the stronger the protection against corrosion. Rusting or corrosion occurs in case the passive layer gets damaged, and the chromium content is not enough to reform it.
But hey, here’s a catch. With routine maintenance and cleaning, the chromium content can stay intact.
Passive Layer’s Function
When chromium content in stainless steel’s surface reacts to oxygen, the passive layer is generated. Acting as a protective barrier, it prevents further oxidation. When compared to carbon steel, upon exposure to oxygen, its surfaces form ferric oxide. Ferric oxide is unable to form a continuous layer. As a result, it eventually chips off, exposing raw steel highly prone to a rusting cycle.
You would be surprised to know that the passive layer, by default, is self-repairing. Upon any exposure to damage, by reacting with oxygen chromium forms a new chromium oxide layer. While there is sufficient chromium content available, the chromium oxide layer will keep on reforming and protecting the SS surface.
Common Corrosion Causing Factors
There are more than 150 grades of stainless steel. Based on their composition, some grades are more corrosion-prone than others.
Anything that diminishes the localised chromium concentration to less than the minimum threshold is bound to cause rusting or staining. Common causes of SS corrosion include hydrochloric acids, chlorides, sulfuric acids, contact with iron/carbon steel and high temperatures. Let’s explore the same in-depth:
- Acids: Strong acids disrupt the passive layer such as:
- Hydrochloric Acids: The acid is popularly used in producing plastic. When SS gets exposed to hydrochloric acids, general surface corrosion tends to occur.
- Sulfuric Acid: It is a corrosive chemical, and it can cause extremely bad chemical burns and secondary thermal burns. Popularly, the acid is used in oil refining, wastewater processing, mineral processing etc.
- Chlorides: Chromium oxide becomes severely vulnerable when exposed to chlorides. Typically, the speed of corrosion is accelerated in regions surrounding the coast, high salt-spray exposure, and in locations where de-icing salts are used typically during winter.
- Iron/Carbon Steel Components: The corrosion can be triggered when the SS surface comes in contact with iron/ carbon steel particles. When left unattended, rusty spots can appear and the chromium oxide surface can corrode. Typically, SS gets contaminated by coming in contact with particles/ sparks coming from nearby cutting, drilling, welding, or grinding workshops (if any).
- High Temperature: SS can also rust if it has been exposed to extremely high temperatures ranging between 750°F-1550°F range. Typically, this corrosion type is seen in welding applications that expose SS to high heat and is cooled down later on. As a result, sensitisation can occur, and carbide formation can take place. This enables grain boundaries to lose chromium. Since the chromium oxide layer doesn’t form, SS gets ruined.
How To Take Care?
Since stainless steel prices are relatively higher, you would want to get the most out of your SS purchases. Worry not, we got you covered. Stainless steel’s life can be enhanced by preventing contact with corrosion-inducing substances. Here are the best practices to increase SS life:
- Always wear clean gloves and leave no room for contamination.
- Keep zero contact with iron or carbon steel.
- Do not cut, drill, weld, grind etc. carbon steel in the vicinity of SS.
- Avoid exposure to chloride solutions.
- Avoid exposure to concrete detergents.
- Never ever use steel wool, abrasive scrubbing pads etc for cleaning purposes.
The most common damages happen when unknowingly people use a corrosive ingredient to clean SS. Under any circumstances, to clean SS products never ever use the following products:
- Abrasive cleaners
- Chloride cleaners
- Chloride bleach
- All-purpose cleaners
Life Enhancing Tips
Here’s how you can take care of SS products:
- When regular maintenance is taken for granted, corrosive substances can gather on SS. Don’t delay regular maintenance.
- Clean it regularly to maintain its pristine appearance.
How To Clean It?
Here are the tips that will help you clean SS products:
- Scrub: Take a soft brush and start by scrubbing away the accumulated dirt/grime using a soft nylon brush. The key is to be gentle.
- Cleanse: The next step is taking a gentle soap/detergent which is SS-friendly and cleansing the surface.
- Rinse: Using clean water, rinse it thoroughly so that any residue can be removed.
- Dry: Only rinsing is not enough, ensuring that it completely dries off. You can use a disposable wipe, or soft cloth to dry the surface.
Over To You
In this article, we have shed light on how to protect stainless steel from rusting using proven cleaning processes. At the time of cleaning, keep in mind to religiously follow all the safety instructions mentioned in the instructions provided with cleaning/polishing products. To be on the safer side, please make sure to wear personal protective equipment so that health and safety guidelines are followed.
SS and mild steel prices are different from each other since their properties and composition vary from each other.