Derustit 4020

Pickling paste transparent

Description & applications

When stainless steel is welded, various oxides and heat discolouration are produced. DERUSTIT pickling paste 4020 is designed to remove such contaminants that could effect the corrosion resis- tance of the metal. This also aids the inspection of the welded joint and adjacent metal. As it is in paste form, 4020 can be applied to vertical welds and to these areas inaccessible to alternative mechanical methods of descaling.

DERUSTIT pickling paste 4020 is intended for use on the Austenitic range of stainless steels and other high Nickel alloys.

Application Instructions

DERUSTIT pickling paste 4020 is intended for use on the Austenitic range of stainless steels and other high Nickel alloys.


Any oil or grease on the surface will impair the pickling action thus the areas to be treated should be cleaned with an alkaline or solvent degreasing agent prior to the application of DERUSTIT pickling paste 4020.

Using the product

The contents of the jar should be thoroughly mixed before use by stirring with a wooden or plastic rod. The paste should then be generously applied with an acid resistant brush (available from DERUSTIT) onto the areas to be treated which should not be warm or in direct sunlight. Treatment time is depen- ded upon the nature and degree of the oxidation required removal. As a guide generally 20-60 minutes (5-20 minutes for Ni or Cu/Ni alloys) at 20°C should prove sufficient, however it may be necessary with heavy oxidation to apply the paste several times. Longer treatment maybe carried out overnight on Austenitic stainless steel without the danger of damage to metallurgically sound material.

1 kg of DERUSTIT pickling paste 4020 has a coverage of 100 linear metres of weld when applied 5 cm wide.

After pickling the paste should be rinsed off with clean water preferably under high pressure. The loosened residues can easily be removed by rubbing with a soft brush if high pressure rinsing is not available. The pickled area should be matt grey in appearance.


A clean stainless steel surface will generate a protective oxide layer in uncontaminated free air. The formation of this „passive layer“ can be accelerated by chemically passivating with DERUSTIT passivating solution 2016.

Effluent treatment

Effluent rinse water resulting from the use of DERUSTIT pickling paste 4020 should be neutralised prior to disposal in accordance with the local water authority regulations.

Safety precausions

DERUSTIT pickling paste 4020 contains Hydrofluoric and Nitric acids and the precautions normally taken when working with acidic solutions should be observed with this product. Protective clothing such as rubber gloves and goggles should be worn. When working in confined or poorly ventilated environments respiratory equipment should be used. More comprehensive safety details are available on the appropriate DERUSTIT safety data sheet.

Please note

The information contained in this data sheet is given to the best of our knowledge and is based upon practical and laboratory tests. Our chemical service department is willing to offer advice on handling, application and process technics.

We are also able to undertake cleaning, pickling and passivating work either at our Dietzenbach works or on-site.

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