treatment of natural stone rust spots

Formation and treatment of natural stone rust spots

1. The formation of rust spots

　　 Rust spots are mainly formed by the oxidation reaction of iron minerals in stone (such as a small amount of iron sulfide minerals contained in some metamorphic rocks). Iron, water and oxygen are the three major factors that contribute to the formation of rust spots. Generally, we divide it into two categories according to the different levels of rust stain reaction:

　　 (1) Deep rust spots. Many types of stone, especially granite, contain a certain proportion of iron components. When these iron components are in full contact with water and oxygen, they will cause oxidation reactions and generate rust spots. Stones that are particularly prone to such rust spots are: Gardenia White Granite, Shandong white (small flower), G682, Yellow Granite,rust stone, etc. In addition, the alkaline substances in the cement for wet laying of stone react with the iron in the stone under the action of water, and also form rust spots.

　　 (2) Surface rust spots. In the process of mining, processing, transportation and installation of stone, a small amount of iron residues will be left after the surface is in contact with iron objects. These iron residues will react with moisture and oxygen in the air to generate rust spots.

Bushhammered Beige Granite

Rusty Yellow Granite

　　 Second, the treatment of rust spots

　　The treatment method of rust spot is mainly to use rust remover to deal with. During the derusting treatment, the following points should be noted:

Sunset Yellow Granite

(1) Try to avoid using oxalic acid to directly clean the stone rust spots, because oxalic acid simply oxidizes and reduces the rust spots (Fe3+). The redoxed iron ions (Fe2+) have instability, which easily occurs again with water and oxygen in the air The oxidation reaction regenerates rust, and further expands the area of the rust spots as the oxalic acid aqueous solution flows. This is why the more rust spots are removed when the oxalic acid is used for rust removal, the larger the removal.

　　 (2) When choosing rust remover, be sure to choose good quality products. Because a good rust remover is added with an appropriate amount of additives in addition to the acid component to maintain the stability of iron ions in the redox reaction. The rust spots treated with this rust remover can be kept for a long time without recurrence even without protective treatment. On the contrary, some rust removers are just a simple mixture of some acids, which cannot maintain the stability of iron ions in the redox reaction and has a high recurrence.

　　 (3) Due to the different composition of marble and granite, the properties are different. The main component of marble is calcium carbonate, which is alkaline; the main component of granite is silica, which is acidic. Therefore, when using rust remover, we must distinguish between marble rust remover and granite rust remover. Granite rust remover must not be used for the treatment of marble rust spots.

　　 (4) For the treatment of surface rust spots, just brush the surface with a rust remover. Sometimes, it can also be treated by surface grinding and polishing; the treatment of deep rust spots is relatively more complicated, and it needs to maintain a certain dose and reaction time. Sometimes it needs to be reused to achieve the desired effect.

　　 (5) After the stone is applied with rust remover, it is recommended to clean it again with clean water. After drying, it must be protected with high-quality stone curing agent. The purpose is to completely remove the residue after the oxidation reaction and prevent the oxidation reaction from occurring again.

　　 3. Prevention of rust spots

　　Prevention of rust spots is mainly carried out by the effective control of the three elements: iron, water and oxygen. The main effective methods of rust prevention are summarized as follows:

　　 1. Before the construction of the stone, it is necessary to use a high-quality stone curing agent to perform six-sided protection treatment on the stone to block the contact between the iron in the stone and the water and the atmosphere.

　　 2. Try to avoid the use of high alkaline cement for stone bonding construction, reduce the chance of the alkaline substance in the cement reacting with the iron in the stone, especially the high-absorption stone material with soft texture.

Xiamen Realho Stone Co., Ltd

Ms.Winnie

Tel: 86-592-8326666  Fax: 86-592-8327777

Email: Sales008@realho.com 

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