What king of material is used to make screws? Can screw rust??

Screws can be made of several materials being plastics , steel,
stainless steel brass, bronze, zinc plated steel

plastic screws obviously can not rust however 
the following materials will corrode when left to the elements for
prologend periods of time

Brass
An alloy of copper with good corrosion resistance. Once common for
marine use, it has been replaced by stainless steel. Used mostly in
decorative applications.

Stainless steel
Stainless steel 18-8 is an alloy of steel with high corrosion
resistance. Stainless has become the material of choice for exterior
and most marine applications.

Zinc plated steel 
Steel is zinc plated for moderate protection against rust. 

Bronze
Bronze is an alloy of copper with greater strength and corrosion
resistance than brass. Most commonly used in wood boat building and
restoration

Steel
Steel bolts are plated for moderate rust protection and available in 3
grades of hardness.

Nice answer, Corwin02 - For dododudu, just go look at your deck -
chances are that at least a few of those screws have had their zinc
coatings nicked off.  They'll be mighty rusty.

Thank you so much for your answer.  The reason why I wanted to know
whether screws can rust is because I am having a dispute with a carpet
cleaning company who came to clean my carpet and upon inspection of
the area I realized the machine left several rust stains on my carpet,
they are permanent and can't be remove. When I told them that the
cleaning machine was leaking and left the stains, their defensive
answer was the machine is made of fiberglass and aluminium and these
materials can't rust.  However, I thought they must be screws holding
the fiberglass and aluminium parts and since the machine was an old
machine, with age and with prolonged contact with hot water, the
screws might eventually rust.  I wanted to make some research as to
what compose screws and whether they can rust before getting back to
them.  Thank you so much for your answer.

For rust stains, I recommend using CLR (available at any home
improvement store/walmart/target/etc).

It is specially formulated as a calcium/lime/rust remover, so that may
help you out if your fight proves to be futile.

Oxi-Clean is also pretty good (also available at target/walmart/etc).

For both, just follow the instructions on the back of the respective packages.

Good luck!  Chances are, that if it's an old machine, it is put
together with zinc plated steel.  However, chances are also that over
time, the zinc has rubbed off.

Hi dododudu,

I owned a Carpet and Upholstery Cleaning company for 7 years.  Don't
worry, rust spots are remarkably easy to remove.  The equipment did
not cause the rust spots, and frankly, it doesn't matter how they
occured.  There is no damage to your carpet.  I recommend changing
your focus.  Simply ask the company to come back and remove the rust
spots.  It takes less than 5 minutes.  If they refuse, remove them
yourself and never use the company again, and --tell all your friends
not to use them.

If you have to do it yourself, you will need this product, or a similiar one:

Rust Remover
http://www.chemspecworld.com/product_detail.asp?par=10&product_id=147

In your local Yellow Pages, look up "Carpet and Upholstery Cleaning
Supplies" and call a couple listings to find it.  No special license
is required.  When you purchase it, ask the salesperson for
instructions.

~~Cynthia

Thank you so much Cynthia.  I will get the product and try it.  It is
a large stain and it looks quite bad.  The carpet company attempted to
removed the stain 4 times  and it is still persistant.  Thank you
again.

Dododudu