Helpful Acids
Even with regular washing after use, dive kit that is used in the sea builds up deposits of 'inorganic salts' (most likely a mixture of loads of sodium, calcium and magnesium salts of nitrates, chlorides, sulfates and carbonates [thanks Trev]). This can have a noticeable effect on regulators and dive computers. Small amounts can be dissolved away with mild acids but some acids will also damage metals.
The chrome coating used to protect metals is prone to flake if too strong an acid is used.
Brass is often used in high pressure areas which have been machined. Brass will react strongly with most acids.
Acetic Acid (aka Vinegar ) is cheap and available in Kit-Monkey friendly sized sachets from pubs. Acetic acid can be a little harsh so metals should not be left soaking. Acetic acid will remove cheap chrome finishes. You can dilute this acid with water.
Citric Acid (aka Lemon Juice). A much milder acid which is fantastic at gentle tasks like cleaning the sensors in dive computers. Over the course of a few dozen dives, a very small build up of salts and grime will make the contacts slightly conductive so the computer will stay in underwater mode for 'longer then it did when new' and ultimately drain the battery!
Fill the smallest bowl possible to just over the depth of your computer. Mix in 2 teaspoons of lemon juice. Wait 30 minutes and you have a (delicious) computer which no longer insists on being in AC (Active Contact) mode.
Kettle cleaner is supposed to be pretty good, it can be a variety of acids but it is generally mild enough to be kind to chrome.
Thicker sauces (ketchup and HP sauce) are acid enough for mild de-scaling. They wont drip like vinegar if the item is too large to submerge and they also encourages a little closer nibbling by fish during your next dive.
Rinse and dry everything before storing.