Can oiling keep tools from rusting?

Question

Even stainless-steel can rust, and I've seen axes and saws that were visibly rusted. I've been told that wrapping the metal parts of the tools in oiled paper will prevent this.

Can oil really be used to prevent rust creation? And is there a difference between types?

From a chemical point of view, I would say it makes sense: The oil and paper wrapping could prevent the access to oxygen and thus prevent oxidation. But I would imagine vegetable oil is vastly different from types meant for engine greasing.

Answer 1

The type of oil surely matters. Within petroleum products, thick, waxy Cosmoline has proven to be effective, but it's not nice to remove. (I've never personally used it for this reason.)

I have recently learned of and started using Fluid Film. It has an unusual (to me) wool-lanolin base. I have limited experience with it and I have not yet conducted my own testing but I have seen several positive reports. You can find tests of varying veracity with a simple Web search.

This is getting further off topic as none of these products are simple oil as far as I know, but here is a salt spray test that includes Fluid Film. Fluid Film is basically non-toxic¹ and performs as about as well as any of the "Soft Film" products. Compare the MSDS² for the highest rated "Water Displacing Soft Film" in that test, CRC Protector 100. For this reason I use Fluid Film for knives/tools that may contact food.

_{1. "Ingestion of this product is not regarded as a significant health hazard likely to arise in normal use."}

_{2. "Harmful or Fatal if Swallowed."}

Answer 2

Ordinary vegetable oils of the type used for cooking will work but are not ideal. Over time they will gradually oxidise and may be colonised by bacteria, both of which can cause them to become acidic which can itself cause corrosion of the metal. Also vegetable oils can become gummy and sticky in quite a short period of time.

Oils help to prevent corrosion by excluding moisture and oxygen from the metal surface. All metals will form a thin layer of oxide on the surface and oil etc can penetrate into this, helping to stabilise it and prevent destructive corrosion.

It's also worth adding that carbon steels will naturally form a blue/grey layer of oxide on the surface and this is not necessarily a bad thing as it can provide a porous surface which can be pretty durable when stabilised with oil or wax.

The best protective oil for a given situation will depend exactly on what you want to achieve. A light oil like 3-in-1 or gun oil is easy to apply and remove and can also be useful as a cleaning agent to remove wood resin etc from a blade. The downside is that its relatively low viscosity means that the protective film formed isn't very durable and so may not be ideal for long term storage or protection during use.

Wax like renaissance wax or simply rubbing with a candle will give a more durable protective film but may need more care in applying to get a thorough coating. Wax can also help to lubricate saws.

Another alternative is grease, this is easy, if potentially messy to apply but should give very good long term protection during storage as it can form a much thicker layer than oil. There are specialist greases for storing metal items which also contain active additional corrosion inhibiting ingredients, although these can be difficult to remove before use. Grease tends to be most useful if something needs to be stored for a significant time in bad conditions.

There is also the consideration that if a tool is to be used for food preparation any protective coating should be reasonably food-safe.

There are also a range of other substances such as silicone or PTFE based greases which can provide some protection from rusting and are available in spray on form or as impregnated cloth wipes. Some of these are intended to leave a dry film which is less prone to attracting dirt and grit and may be an advantage for tools such as folding knives with exposed moving parts and bearings.

Overall I would say :

• Oil is good for routine maintenance of frequently used tools, eg wiping on a thin film after use or for tools with complex assemblies or moving parts where penetration into small spaces is required.

• Wax is good for storage of occasionally used tools in reasonably good conditions. Or if a tool is being used outdoors in wet weather.

• Grease is good for long term storage in poor conditions eg tools only used for part of the year and kept in a shed.

• Tools with fine mechanisms may benefit from dry film lubricants to reduce the risk of attracting grit etc.

Answer 3

It can, yes - by keeping water and oxygen away it can greatly slow or prevent the oxidisation process from occurring.

However, I wouldn't necessarily advise it as the best approach. Instead I'd advise making sure tools are clean and thoroughly dry, then storing them in a cool dry place (unless the manufacturer recommends otherwise of course.)

There's two main reasons for this. Firstly, oils can go rancid, which means they're a) not as effective at keeping out moisture and oxygen and b) they smell absolutely foul. Secondly, some oils - notably vegetable and mineral oil - can leave a horrible sticky residue which is a nightmare to clean off.

There may be corner cases with situations or bits of kit that makes it worth it, but in general I'd say it can do more harm than good.