How to choose anti-corrosion materials for dust collectors

In industrial production, dust collectors are key facilities for controlling dust pollution and ensuring air quality. However, dust removal equipment is exposed to complex media containing dust, acid and alkali gases, water vapor, etc. for a long time, which is very prone to corrosion, leading to equipment failure, reduced operating efficiency and even safety accidents. The rational selection and application of anti-corrosion materials are the core links to improve the durability and reliability of dust removal equipment. Starting from the corrosion mechanism of dust removal equipment, this article systematically analyzes the selection principles of anti-corrosion materials, the characteristics of common materials and typical application scenarios, and provides a reference for engineering practice.

1. Dust collector corrosion mechanism and environmental characteristics

(I) Main corrosion types

The corrosion of dust collectors mainly includes chemical corrosion, electrochemical corrosion and wear corrosion. Chemical corrosion originates from the direct reaction of acidic gases (such as SO₂, HCl, NOx) with the equipment surface to form corrosion products such as sulfides and chlorides; electrochemical corrosion is caused by the presence of electrolyte solutions (such as condensed water, dust moisture absorption layer) on the metal surface, forming micro-batteries that lead to local corrosion; wear corrosion is caused by dust particles scouring the metal surface at high speed, destroying the protective film and causing corrosion to intensify.

(II) Typical corrosion environment

High humidity sulfur-containing flue gas environment: Flue gas dust removal equipment in coal-fired power plants and waste incineration plants is exposed to high-temperature flue gas containing SO₂ and water vapor for a long time, which is prone to sulfuric acid corrosion.

Strong acid and alkali chemical environment: Acidic waste gas (such as sulfuric acid mist, hydrochloric acid mist) or alkaline dust (such as sodium hydroxide dust) in the chemical and pharmaceutical industries has strong chemical corrosion on the equipment.

High dust and abrasion environment: Dust removal equipment in the mining and building materials industries has high dust concentration and hardness, which accelerates metal surface corrosion during the scouring process.

2. Principles for selecting anti-corrosion materials

(I) Medium compatibility

The material needs to be chemically inert to specific corrosive media. For example, when exposed to sulfuric acid fume, materials resistant to sulfuric acid corrosion should be selected; when exposed to chloride ion environment, ordinary stainless steel (prone to pitting) should be avoided.

(II) Working temperature adaptability

The temperature resistance range of different materials varies significantly. For example, the temperature resistance of rubber lining is usually below 120℃, while polytetrafluoroethylene (PTFE) can be used for a long time at -200~260℃. It needs to be reasonably selected according to the operating temperature of the equipment (such as high-temperature flue gas dust removal requires a temperature resistance of ≥200℃).

(III) Mechanical properties and construction convenience

The material needs to have sufficient strength, wear resistance and impact resistance, and the feasibility of the construction process (such as spraying, lining, welding) should be considered. For example, fiberglass reinforced plastic (FRP) is easy to form, but it is brittle and should be avoided in high vibration scenarios.

(IV) Economic efficiency and life cycle

Comprehensively consider material cost, maintenance cost and service life. For short-term projects, cost-effective rubber linings can be selected, while for key equipment in long-term operation, corrosion-resistant alloys or composite coatings should be used.

3. Commonly used anti-corrosion materials and their characteristics

(I) Metal-based anti-corrosion materials

Stainless steel

Features: 304 stainless steel is resistant to atmospheric corrosion, 316L stainless steel is resistant to chloride ion corrosion, and 904L stainless steel is resistant to strong sulfuric acid corrosion; it has good high temperature resistance (≤600℃), but the cost is relatively high.

Application: Bag filter housing of coal-fired power plants, main structure of acid mist purification tower in chemical industry.

Corrosion-resistant alloys

Features: Hastelloy is resistant to strong acid and alkali and high temperature corrosion, and titanium alloy (TA2) is resistant to chloride ion and seawater corrosion, but it is difficult to process and expensive.

Application: High-temperature flue gas dust collector in waste incineration plants, desulfurization and dust removal equipment in coastal areas.

(II) Non-metal-based anti-corrosion materials

Fiberglass reinforced plastic (FRP)

Features: It is a composite of resin (such as vinyl ester, epoxy resin) and glass fiber, with excellent acid and alkali resistance, low density, and easy molding; but it has average temperature resistance (≤150℃) and is easily aged by ultraviolet rays.

Application: Acid waste gas washing towers in the chemical industry, small and medium-sized dust removal equipment pipelines.

Rubber lining

Features: Natural rubber is resistant to water and weak acid, butyl rubber is resistant to acid and alkali, and chloroprene rubber is resistant to solvents; good elasticity, can absorb dust impact, temperature resistance ≤120℃, and is easily corroded by organic solvents.

Application: Steel plant blast furnace gas dust collector, coal mine coal washing plant dust removal pipeline lining.

Engineering plastics

Features: Polyvinyl chloride (PVC) is resistant to medium concentrations of acid and alkali, polyethylene (PE) is resistant to low temperature corrosion, polytetrafluoroethylene (PTFE) is resistant to strong acid and alkali and high temperature (260℃), but has low hardness and is easy to creep.

Application: PTFE is used for filter bag frames in chemical high temperature and strong corrosion environments, and PVC/PE is used for normal temperature acid and alkali waste gas pipelines.

(III) Composite coating materials

Glass flake coating

Features: Epoxy resin is used as the base material, and glass flakes (diameter 50~300μm) are added to form a dense coating with strong impermeability and temperature resistance ≤200℃, which can effectively prevent the penetration of corrosive media.

Application: Corrosion protection of the inner wall of the flue gas desulfurization tower of power plants and the box of large dust removal equipment.

Ceramic coating

Features: Alumina (Al₂O₃) and silicon carbide (SiC) coatings have high hardness (Mohs hardness 9), high temperature resistance (above 1000℃), and both wear resistance and corrosion resistance, but they are brittle and costly.

Application: The inner wall of the dust collector of the mine crusher, and the high temperature and high dust scouring area.

4. Application practice under different working conditions

(I) High temperature sulfur-containing flue gas environment (such as power plant boiler dust removal)

Corrosion characteristics: Flue gas temperature 150~200℃, containing SO₂, H₂O, easy to form sulfuric acid condensate.

Material solution: The box body uses Q235B + glass flake coating (thickness ≥1.5mm), the filter bag frame uses 316L stainless steel, and the flue is lined with acid-resistant bricks (such as acid-resistant ceramic bricks).

(II) Strong acid and alkali chemical environment (such as fertilizer plant dust removal)

Corrosion characteristics: The medium contains hydrochloric acid, nitric acid, ammonia water, normal temperature or low temperature (≤80℃).

Material solution: The washing tower is integrally formed with FRP (vinyl ester resin), the pipeline is lined with butyl rubber, and the valve uses PTFE lined ball valve.

(III) High dust and abrasion environment (such as cement plant raw material mill dust removal)

Corrosion characteristics: high dust (CaO, SiO₂) concentration, high hardness, scouring speed 15~25m/s.

Material solution: The elbow and guide plate of the dust collector adopt wear-resistant ceramic patches (thickness 5~10mm), and the main structure is sprayed with tungsten carbide alloy coating (hardness ≥HV1000).

5. Key points of anti-corrosion construction and maintenance

(I) Surface treatment

Before construction, the metal substrate needs to be sandblasted to remove rust (reach Sa2.5 level), remove oxide scale and oil stains, and ensure that the bonding strength between the coating and the substrate is ≥5MPa.

(II) Process control

Glass flake coating needs to be constructed in 2~3 layers, with an interval of 24 hours between each layer; the rubber lining adopts hot vulcanization process (150℃×4h) to avoid bubble residue.

(III) Regular inspection

The integrity of the anti-corrosion layer is regularly checked by coating thickness gauge (thickness deviation ≤10%) and spark leak detector (voltage ≥5kV), and damage is repaired in time.

6. Conclusion

The selection of anti-corrosion materials for dust removal equipment is a systematic project, which needs to comprehensively consider the medium characteristics, temperature, mechanical properties and economy. With the improvement of industrial emission requirements, anti-corrosion materials will develop towards high performance (such as extreme temperature resistance, ultra-long life), environmental protection (solvent-free coatings, recyclable materials) and functional composite (wear resistance - corrosion resistance - thermal conductivity integration) in the future. In engineering practice, targeted plans should be formulated in combination with specific working conditions, and through scientific material selection, standardized construction and meticulous maintenance, efficient and stable operation of dust removal equipment can be achieved, providing guarantees for the green development of industry.