How to clean Stainless steel: a comprehensive guide
Cleaning Stainless steel is vital for not only preserving and enhancing the aesthetic value of the Stainless, but also for preserving the corrosion resistance of the material. Contamination of the surface by dirt or anything else hinders the natural passivation process of the Stainless steel and traps corrosive agents, reducing corrosion protection.
How you clean your Stainless, especially when it requires intensive cleaning, will depend on multiple factors. It is possible to damage your Stainless if you use the inappropriate chemicals or abrasives, so keep reading to learn how to properly clean your Stainless, preserving its aesthetic value and corrosion resistance.
Cleaning and the longevity of Stainless steel
Stainless steel has excellent longevity. With the design and selection, fabrication, handling and maintenance, installations can reach a lifespan of 50 years or more without replacement. This blog will go into detail on this; but generally, the easiest way to maintain your Stainless is simply a frequent gentle clean with water and detergent. Even with no visible soiling, cleaning your Stainless regularly (weekly, the more frequent the better), clears any contaminants not visible to the naked eye and preserves the oxide layer, keeping your Stainless looking good and corrosion resistant for longer without the need for deeper cleaning. As they say, prevention is the best medicine, and the same applies to your Stainless!
General light cleaning of Stainless steel of all types
Although different types of Stainless and different levels of contamination require different methods of cleaning, in general, all Stainless steel benefits from a frequent water and wipe clean. Stainless surfaces thrive with frequent cleaning because there is no surface coating to wear off. A soft cloth and clean warm water should be the first choice for mild stains and loose dirt, with a final rinse with clean water and a dry wipe leaving a water stain-free result..
Use warm water and optionally a mild detergent to clean, with a clean non-abrasive sponge, rag or microfibre cloth.
Use gloves when cleaning, avoiding smudging and fingerprints.
After cleaning, rinse thoroughly with water.
Completely dry the Stainless after cleaning with a dry towel (especially when using water which contains mineral solids, like tap water).
Avoid water staining and limescale build up by thoroughly drying your Stainless after cleaning.
Always avoid these cleaning mistakes!
There are some methods of cleaning to always avoid, as they will damage the Stainless surface, leading to corrosion, or can be harmful to you.
Never use oily rags or greasy cloths.
Never clean with chloride-containing detergents or sodium hypochlorite-based bleaches.
Never use steel or metal abrasives. If abrasives must be used, scotch-brite or Stainless steel wool only.
Never use hydrochloric or sulphuric acids.
Never use solvents in enclosed spaces or anywhere near fire.
Never use halogenated solvents. i.e. those containing fluorine, chlorine, bromine, iodine, or astitine.
Never mix cleaning chemicals without the appropriate knowledge or proper professional advice.
Never use any abrasives, solvents or other chemicals on the inappropriate Grade/polish or without knowing what Grade/polish your Stainless is (read below).
Don’t trust just any label that states “for Stainless steel”. It’s no guarantee that the product is not abrasive, not acidic, or low in chlorides! Always do your proper research on Stainless steel cleaners.
A note on abrasives
Although abrasives can be effective in removing tough stains and soiling, they can do real damage to Stainless steel, including not only leaving cosmetic scratches but also damaging the protective passive layer, leading to discolouration if the layer is not quickly replenished. Abrasives should never be used on coloured and highly polished/annealed finishes, as they cause permanent damage, ruining their aesthetic appeal. Thus, extreme care should be taken before choosing to use any abrasive on Stainless steel, including research on the abrasive, identifying the finish you are dealing with, and patch testing.
Also consider grain and scratch direction when using abrasives. For example, a circular rubbing pattern on a surface with longitudinal scratches (most ‘satin’ type finishes) will be clearly visible, even when the circular pattern is of a milder coarseness.
A note on passivation
Although passivation is a way to renew Stainless steel, it is not a form of cleaning and shouldn’t be confused with pickling, which is a post-fabrication finishing process in which residual iron particles left behind from machining are removed via prolonged immersion in an acid solution bath. It can be the next step to restore the passive layer of Stainless steel after a thorough cleaning. Passivation is technically specific and requires time and temperature control – as it is its own topic in itself, we will explore pickling and passivation in detail in a future blog.
Safety in cleaning
Any use of strong chemicals requires the appropriate safety precautions, as these chemicals can be toxic to humans if breathed in heavily or accidentally ingested. Always follow the guidelines as set out per the packaging, wear gloves and the appropriate safety gear, depending on the chemical/cleaning compound that you are using. The below advice should be followed at your own discretion, and you should ensure your own health and safety before engaging in any Stainless steel cleaning.
Household v Commercial cleaners (and Stainless steel Grades)
Household
Stainless steel Grades in the household and Stainless for commercial use can overlap, but can also differ, with higher Grades of Stainless generally found outside the household.
In the household, Stainless steel will generally be Grade 304. This can apply to appliances, kitchenware like sinks, taps and cabinet knobs, and can be found in the bathroom also on taps, towel racks and other built-in pieces. Occasionally it can be found in other areas of the house, like doorknobs, hinges, etc. Household Stainless will not likely come into contact with extremely corrosive materials, but may experience light soiling from dirt, grease, fingerprints, limescale or more severely, baked on food or grease build up, like in the inside of the oven or on the stovetop.
Household cleaners fall into two categories: detergent (non-abrasive) and abrasive cleaners. These can be effective for dirt, mild stains, and soil deposits and fingerprints. The abrasive cleaners are more effective but there is a possibility of scratching the surface. For food grease and limescale, household cleaners like vinegar, baking soda or Bar Keepers Friend are safe to use on Stainless. You can also try a pre-made degreaser, just do your research first to ensure that it is safe on Stainless.
Detergent, vinegar, baking soda and household degreasers/cleansers can be used to remove grease in the household. Always do your research on pre-made cleansers.
Commercial
Commercial use Stainless steel comes in a great more variety of Grades due to having to withstand much more corrosive environments compared to the household. Uses can range from the Food & Beverage industry, to automotive, to architectural, to marine, to aerospace and everything in between. These uses will have different polishes and Grades, so the proper research needs to be done both in selecting the correct Grade and polish beforehand to ensure it can and will be cleaned and maintained, as well as using the the correct methods of cleaning which can vary.
Many commercial cleaners compounded from phosphates, synthetic detergents, and alkalis are designed for heavy soiling, staining and surface corrosion. Different products will have different uses, and can be used singularly or in combination depending on the situation. In general, commercial cleaners will be more hazardous due to being stronger than household cleaners, so extreme care and safety precautions should be taken when using them. Manufacturers should be consulted and their recommendations followed whenever using cleaners of this kind.
Industrial food production can include consistent exposure to acids and chlorides, so the right Grade should be selected to prevent corrosion, and stronger cleaning chemicals can remove any corrosive residue.
Selecting your finish and cleaning it
Beyond Grade choice, finishes have a great effect on the appearance and functionality of Stainless steel.
We have a full guide on Stainless steel finishes, which you can read here.
Depending on the use, different finishes will be selected, and these finishes have different methods of cleaning.
Mirror polished Stainless steel, used in architecture.
Mirror polished Stainless presents a stunning option for aesthetic uses, however can be easily soiled by fingerprints, sullying its visual appeal. There are several special surface finishes where fingerprints present special problems: polishes denoted No. 6 - No. 8, etched, some abrasive blasted finishes, and light electrochemical colours applied over satin or brushed finishes. Thus, effort should be taken to only use these types of finishes where the Stainless is not regularly touched by people or can get dirty easily. In addition, scratching can occur on a bright mirror finish by cleaners that contain hard abrasives, or even by “grit” in wash water, so abrasives should absolutely never be used on these surfaces.
Balustrade finished with #320 grit polish.
On duller finishes, or those surfaces finished with a coarse polishing grit, regular touching presents less of a problem. Fingerprint marks don’t show up clearly and tarnish visual appeal, thus courser grits are recommended for uses like balustrades, appliances or other Stainless surfaces that are regularly touched. There are several special finishes designed to withstand fingerprints: embossed, swirl patterns, lined patterns and more. Courser grits can withstand more vigorous cleaning, but should only ever be cleaned along the polish lines, never against them.
Stainless steel grain up close. Always clean in the direction of the grain. In this case, left and right not up and down!
Preparing your Stainless cleaning kit
Mention of products by name does not indicate their sole suitability for solving the specific problem — others in the same product type classification may prove to be equally effective.
Household cleaning products
As stated above, your basic Stainless steel clean up needs require some
Detergent (a.k.a regular dish soap);
a microfibre cloth or sponge;
and a towel to dry off.
This should get most basic cleaning jobs done in the household and some commercial uses. As an addition for built up grease in the kitchen:
Vinegar;
baking soda;
household degreaser/cleanser.
The below video is a guide to cleaning household appliances with these products.
Commercial cleaning products
Getting into commercial use, for many cleaning applications, you can use the same methods as household cleaning, however there will be situations where something stronger is necessary. There are pre-made Stainless steel cleaners that are designed for more heavy soiling in these settings.
Compound cleaners
One compound cleaner that is suitable for Stainless steel is 3M Stainless Steel Clean & Polish, which we stock in the Stirlings Superstore.
The 3M Stainless Steel Cleaner and Polish cleans Stainless steel surfaces and also leaves a high gloss finish. The formula won't leave streaks or build up and masks surface blemishes. It meets the requirements of the NSF Nonfood Compounds Registration Program for metal cleaners and polishes for nonfood contact surfaces.
Watch a guide to 3M Stainless Steel Clean & Polish below.
3M Stainless Steel Clean & Polish Info Sheet
Non-abrasive sponges/pads
Also effective is the Scotch-Brite pad, which can be used to scrub tough stains without damaging the Stainless.
Solvents
egarding heavy grease and oils, non-halogenated solvents can be used in addition to detergent and water to clean. A non-halogenated solvent is an organic compound that does not contain any halogen atoms (fluorine, chlorine, bromine, or iodine) in its structure, and thus does not corrode the surface of the Stainless. These include:
acetone,
methyl alcohol,
ethyl alcohol,
methyl ethyl ketone,
benzene,
isopropyl alcohol,
toluene,
mineral spirits,
or turpentine.
If using any of these solvents, strictly follow the instructions and safety guidelines as per the packaging. Also, do not leave the solvent on the Stainless steel for extended periods - once the soiling is removed, wash immediately with water and dry thoroughly. Keep solvents out of contact with hands and skin. All solvents should be used only in well-ventilated places as their vapours are toxic to breathe for extended periods or in high concentrations. Always wear rubber gloves when working with these cleaners.
Rust Removal
When getting to the level of rust removal, specialist products are required, and this cleaning only applies to surface rust staining, also known as tea staining, not any deep structural damage. These chemicals should be used with extreme care. If not comfortable with engaging in rust removal yourself, contact a licensed contractor.
Compound rust removal agents
One of these is Innoshine B570, a rust remover stocked in the Stirlings Superstore.
It is a special deep cleaner (not a pickling agent) that removes oxides from Stainless steel. Consisting of organic acids and surface-active agents, it is free from abrasive particles.
Acids
Acids are dangerous and for on-the-job cleaning should be used only as a last resort. Synthetic rubber gloves should be used, and goggles and aprons are advisable. Acid cleaners may possibly harm paint, wood or fabrics and stain concrete, galvanised steel and other metals; avoid contact with such materials when using them on Stainless. Before an acid cleaner is wiped on a Stainless steel surface, the surface should always be rinsed with an ample amount of clean water, preferably hot. This is done to wash away chlorides which, if present, would cause etching and white spotting. This precaution is generally not necessary when the item can be immersed in a large volume of acid.
The acids suitable for Stainless steel are the following:
Phosphoric acid;
Oxalic acid;
Sulfamic acid; or
Nitric acid.
These acids should always used at a 10% dilution (1 part acid to 9 parts water) when used to clean Stainless steel. Leave the acid for 30-60 minutes on the rust affected area, and completely clean the acid off with water. Also rinse your drains thoroughly.
Aftercare
After cleaning is complete, you can engage in aftercare of your Stainless to have it looking great and preserving its natural corrosion resistance.
Treatment
Post-cleaning treatments help protect and maintain the passive layer of the Stainless, promoting ongoing corrosion resistance.
One product you can use for this is Innocare B580, which we stock in the Stirlings Superstore.
Innocare B580 works as a post-rust removal cleaner (to be used after Innoshine B570) and treatment in one. Next to its deep cleaning properties, it will provide the metal with a nano-scale protective layer, aiding in its corrosion resistance in future use. The video above shows Innocare B580 in use.
Polish
Stainless steel polish is used to restore and enhance the appearance of Stainless steel surfaces, leaving a bright, streak-free finish.
One product that can be used for this purpose is Ferro’s Liquid Reflection Metal Polish, which we stock in the Stirlings Superstore. Ferro’s Liquid Reflection contains a soft fine alumina to gently polish and restore metal surfaces. It is ideal for polishing jobs done by hand, creating a lustrous shine.
Apply a small quantity to a clean soft clothand rub the surface. The longer the rubbing, the brighter the surface becomes. Wipe dry with a clean cloth to observe the brightness.
Type of contaminants and how to clean them
Once you have understood your products, have your kit ready and have your safety precautions in place, let’s get to cleaning. The below is a guide on different levels of soiling and how to clean. If these methods do not prove effective in your particular case, please contact a licensed contractor.
Mild soiling
How to clean chlorides off Stainless steel
Spray an ample amount of warm or hot water from a hose on to the Stainless steel.
Wipe the surface completely with dry towels.
Chlorides
Chlorides (salts) can only be cleaned off in this manner before they have started to cause rusting.
De-icing salts can also be removed in this way.
Dirt
Dirt, dust and soil can consist of various contaminates that come from many sources.
These contaminates will vary greatly in their effect on appearance and damage to the passive layer, and ease of removal.
How to clean dirt off Stainless steel
Wipe down the surface or immerse small parts in soap or detergent and water and a cloth.
If this does not remove the dirt, try utilising baking soda and vinegar in addition. Clean with a soft rag until the dirt is removed.
Rinse in clean warm water.
Wipe the surface completely with dry towels.
Medium soiling
Fingerprints, smears and mild stains
Fingerprints and mild stains are the most common surface contaminates. They usually affect only appearance and rarely have an effect on corrosion resistance.
Fresh fingerprints, oils and greases should be removed promptly, as if they are left for extended periods they have to potential to damage the passive layer and lead to oxidisation.
How to clean fingerprints, smears and mild stains off Stainless steel
Wipe down the surface or immerse small parts in detergent and water.
If this does not remove the fingerprints/smears, utilise a specialty compound cleaner, such as 3M Stainless Steel Cleaner & Polish. Alternatively, a non-halogenated solvent can be used.
Clean with a soft rag or non-abrasive sponge, such as Scotch-Brite, until the marks have been completely removed.
Rinse in clean warm water.
Wipe the surface completely with dry towels.
Shop oil and grease
Shop oils, which may carry grease, grit and metal chips, commonly produce surface soiling after many shop operations. Greases and other contaminates may also soil surfaces in food preparation and many other household and commercial situations.
Oil and grease can be difficult to remove due to their slick and viscous nature. They may be corrosive in themselves, so periodic removal is a necessity.
How to clean shop oil and grease off Stainless steel
Wipe down the surface or immerse small parts in detergent and water.
If this does not remove the grease, utilise a compound cleaner, such as 3M Stainless Steel Cleaner & Polish. Alternatively, a non-halogenated solvent can be used.
Clean with a soft rag or non-abrasive sponge, such as Scotch-Brite, until the grease has been completely removed.
Rinse in clean warm water.
Wipe the surface completely with dry towels.
Severe
Scratches
On bright annealed 2B and 2D, high-pol or coloured finishes, scratches cannot be removed successfully. Get in touch with a contractor to talk about how best to restore your Stainless in these cases.
On duller finishes, a Scotch-Brite pad can be used in the direction of polish lines.
How to clean scratches off Stainless steel
Wearing gloves, wipe down the surface or immerse small parts/tools in water.
Scrub with non-abrasive sponge, such as a Scotch-Brite pad, in the direction of the polish lines, until scratches have been removed.
Rinse in clean warm water.
Wipe the surface completely with dry towels.
Rust stained flat surfaces
The brown surface stains on Stainless steel are cosmetic rust stains. This ‘tea staining’ will not progress to potential structural damage as could occur with a carbon steel structure.
Early action after the onset of tea staining is necessary, before the underlying surface is damaged.
It is not common to get to the point of Stainless steel rusting/tea staining, and it can indicate inadequate care or that the correct Grade and/or polish was not selected for the application. The following steps may be taken to prevent recurrence:
Increase the frequency of maintenance.
Engage a contractor to provide mechanical polishing and a chemical treatment.
Replace with a more suitable grade of Stainless steel.
How to clean rust stained flat surfaces on Stainless steel
Rinse the surface or immerse small parts/tools in water.
Apply a rust removal chemical compound, such as Innoshine B570. Apply as per the packet instructions. Alternatively apply a 10% solution of either oxalic, phosphoric, sulfamic or nitric acid and leave for 30-60 minutes, depending on the level of tea-staining.
Clean with a soft rag or non-abrasive sponge, such as a Scotch-Brite pad, until the tea staining has been completely removed.
Rinse thoroughly in clean warm water.
Wipe the surface completely with dry towels.
Too severe - when the damage is too extreme for just cleaning
Stainless steel can reach a level of corrosion that is too severe for just cleaning. At this point, mechanical electropolishing followed by passivation would be used to repair the Stainless steel. This would occur in the case of:
Pitting corrosion;
Any rusting that goes beyond the level of tea-staining;
Rusting that occurs in extremely corrosive environments (i.e. marine).
After mechanically cleaning off tea staining, it is preferable to passivate the surface by using a nitric acid gel or by immersion in a nitric acid bath. Passivation is very strongly recommended for marine use.
If there is any structural damage to the Stainless steel, it needs to be replaced immediately.
Stainless steel aftercare
After cleaning your Stainless, treatments and polishes help restore the aesthetic value as well as the corrosion resistance the surface.
How to treat Stainless steel / how to polish Stainless steel.
For both treatments and polishes, utilise a commercially available pre-made compound mixture, such as Innocare B580 (treatment) and Ferro’s Liquid and Metal Polish. For best results, follow the instructions as set out by the packaging, and always apply in the direction of the grain.
If you possess a handheld power buffer, this can be used after your polish, enhancing the shine.
A beautiful shine on some Tube Fittings!
Products in stock at Stirlings
As stated, we stock a range of products in our Stirlings Superstore for every stage of cleaning. These are tried and tested products specifically designed for Stainless, so you can be sure you are not risking damaging your Stainless with these products and giving it the best possible care.
Cleaning: 3M Stainless Steel Cleaner & Polish
Rust removal: Innoshine B570
Treatment: Innocare B580
Polish: Ferro’s Liquid Reflection Metal Polish
A rhyme for your time
The look of your Stainless making you whine? Follow this guide, and all will be fine!
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