What are the types of rust spots on stone? How to handle it

The exterior wall of the villa is made of granite fire panels, which have severe rust spots. The yellow rust granite fire panels have been in use for over 5 years. And the board has not undergone any protective treatment after installation. After prolonged exposure to sunlight and rain, rust spots are produced.01

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Causes and classification of stone rust spots:


To treat a disease, the first step is to understand its causes, and then to achieve targeted treatment. The causes of rust spots on general stone materials are roughly as follows: iron elements (Fe) in the stone or environment undergo oxidation reactions with water (H20) and oxygen (O2), resulting in rust spots on the surface of the stone.
Rust spots can be roughly divided into three types:
(1) Primary rust spots;
(2) Secondary rust spots;
(3) Integrative rust spots. The rust spots in this case belong to the first type.

The Principle of Stone Rust Spot Treatment


(1) By using chemical reducing agents to reduce trivalent iron ions to divalent iron ions, the yellow brown insoluble trivalent iron ions are transformed into colorless and water-soluble divalent iron ions.
(2) Stabilize with chemical stabilizers to prevent the oxidation of divalent iron ions to trivalent iron ions.
(3) Use the application method to adsorb residual divalent iron ions.
(4) Remove residual iron ions through multiple “water spray drying” processes.

The treatment process for stone rust spots:


1. Finished product protection: Use plastic film (or protective film) to cover and protect the construction area and surrounding items, and pay special attention to not letting the treated medicine and cleaning sewage flow into the flowers and plants, otherwise it may cause environmental pollution. In addition, prepare two or three buckets on site, each containing half a bucket of clean water for backup.
2. Cutting and blocking: Isolate the main source of pollution causing the disease from the stone material to prevent recurrence during and after treatment. The main source of pollution in this case is rainwater, so construction should be carried out in sunny weather to avoid rainwater pollution
3. Clean stone: Use dry cleaning to clean and dry the surface of the stone.
4. Release Protection: For the solvent type of stone protective agent, select the corresponding chemical agent to release the protective effect of the stone. (The stone in this case has not undergone protective treatment. If protective treatment has been applied, DEC 21 can be used to remove the surface protection of the stone, which is conducive to the penetration of the treatment agent.)
5. Suit the remedy to the case: Use tools such as a brush, bristle, or roller to apply chemical agents to the rust spots on the surface of the stone.
(1) Clean rust spots with granite rust remover (2-3 times).
(2) Clean the residue with a super oxidizing detergent (2-3 times).
(3) Clean the residue again with a universal stain remover (2-3 times) until the rust spots on the stone surface are completely removed.
(4) After each application of the medicine, cover it with white cotton or non-woven fabric and add the medicine to moisturize it (without forming a flow).
(5) Cover with plastic film and flatten with a roller.
(6) After each application of the agent, wait for 2 hours and uncover a corner to check the condition of the rust spots on the stone. If all the rust spots are removed, remove the cover and soak it in a pre prepared bucket; If the rust spots are not completely treated, repeat the “targeted treatment” step until the rust spots are completely treated.
6. Remove the liquid medicine: Use a spray can to spray clean water onto the surface of the stone to remove any remaining liquid medicine. Repeat this step 3-4 times until the surface is neutral (tested with a pH test paper). Dry with a hair dryer.
7. Antioxidant treatment: Brush the antioxidant onto the surface of the stone with a bristle and let it dry, which can prevent the oxidation of iron elements.
8. Protective treatment: Apply composite nano siloxane protective agent (or stone penetration protective agent), and maintain the curing time for 48 hours at room temperature. For every 10 ℃ decrease in temperature, the curing time should be extended by 2-4 times. This can prevent water from seeping into the stone, thereby generating rust spots again.
9. Site clearance treatment: Remove finished product protection and properly dispose of construction waste.
10. Precautions:
(1) Do not work in natural environments such as high temperatures, direct sunlight, and rain.
(2) According to the on-site environment, protect and construct in sections, and keep an eye on the weather conditions at all times.

Preventive measures in the later stage:

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1. Every year, protective measures are taken to prevent external pollution sources from infiltrating the stone.
2. Isolate sources of pollution and avoid direct contact between metals and stones.
3. External wall cleaning should use stone specific cleaning agents, and acid cleaning with solutions such as hydrochloric acid, sulfuric acid, and nitric acid is prohibited.
4. When rust spots appear again, special chemical agents for stone materials should be used in a timely manner to avoid expanding the pollution range and worsening the rust spots.

Post time: Jul-24-2023

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