How to choose a descaler for limescale and rust: pH and material

To remove limescale and rust you almost always use an acid product, but not all of them suit every material. For coffee machines and circuits, choose a descaler designed for the required use; for welded stainless steel, a pickling gel; for rust stains on metals and hard surfaces, a deoxidiser. In the collection the pH ranges from less than 1 to 14: read it, because it tells you how aggressive the product is and what you can use it on.

The types

• Acid descaler: dissolves limescale. Examples: Fe 50 by Firma Chimica, an industrial descaler, DECAL RC for coffee machines (food use) and Decal RA for car and truck radiators.
• Concentrated descaler: diluted according to the label, for surfaces and equipment. Example: WIPP HD.
• Deoxidiser and rust remover: they remove rust stains, like OXY OUT GEL. A rust converter, on the other hand, does not remove it: it turns it into a stable layer.
• Pickling agent: removes oxides and processing residues. Decap Gel acts on weld oxide on stainless steel; Decap OT on yellow alloys and steels.
• Wax stripper: Decer Super is a low-foam concentrate for removing waxes and stubborn dirt.

How to choose by job

In practice the choice is made in two steps. First work out what you need to remove: limescale (white or greyish deposits), rust (orange or brown stains), weld oxide (a halo on stainless steel) or mixed dirt. Then check the material: stainless steel, iron, yellow alloys such as brass, fibreglass, stone. A product that suits iron is not necessarily right for stone.

The features to look at

• pH: from less than 1 to 14 in the collection. Values close to 1 are strong acids, for stubborn limescale and oxides; a pH of 14 is an alkaline product; 7 is neutral and gentle. The lower the pH, the more you need gloves and care with materials.
• Density: between about 1.035 and 1.325. It indicates how concentrated the product is; it is mainly useful for dosing dilutions.
• Appearance: liquid, viscous or gel. Gel is better on vertical surfaces and for localised treatments; liquid for immersion and circuits.
• Versatility: on metals, fibreglass and gelcoat, or on porous materials. Read it first, because the wrong acid ruins the material.
• Size: from 200-400 ml spray cans to 5 and 10 litre jerrycans. Spray is fine for spot jobs, the jerrycan for daily use.
• Smell: from odourless to pungent. If you work indoors, ventilate.

Common mistakes

• Not testing first. Marble and delicate metals can be attacked: test on a concealed area.
• Letting the product dry on the surface. It must stay wet while it works.
• Mixing different products. Never combine an acid with another product.
• Forgetting to rinse, which must be done generously.
• Working without gloves and safety glasses. Strong acids burn skin and eyes.
• Choosing by name alone. Descaler, pickling agent, deoxidiser and converter do different things: read the use stated on the label.

Frequently asked questions

Can I use a descaler on marble?

Normally not: acids attack marble. Check the data sheet and always test on a concealed spot.

What is the difference between a deoxidiser and a rust converter?

The deoxidiser removes the rust; the converter turns it into a stable layer that can be painted over.

Does a low pH mean a better product?

No, it means a more aggressive one. A strong acid works quickly but requires more caution with materials; for light dirt a milder product is enough.

Can I dilute the product?

Only if the label allows it. Concentrates are diluted; ready-to-use products are not.

Do I need a special product for the coffee machine?

Yes, use a product designated for food use and rinse carefully.

You will find all the products in the Scale and rust collection; to choose the right one for your material, ask for a quote or advice from the AMES technicians.