Several aspects of automobile corrosion and dirt analysis:
(I) Paint diagnosis
1. Paint diagnosis is to determine the problems with the paint surface and find solutions.
(1) Paint contamination analysis
Paint contamination is usually caused by factors such as acid rain, industrial pollution, and ultraviolet radiation, including the following two aspects:
1) Surface contamination: including dust, tree gum, asphalt, fresh bird droppings, industrial emissions, static electricity adsorption, and flying paint.
2) Deep contamination:
Rain corrosion: caused by acid rain, local darkening and roughness.
Settled oxidation layer: formed by long-term sunlight exposure, making the car paint appear dull and lose its luster, affecting the waxing effect.
Micro scratches (stripes, swirls): improper car washing or computerized car washing causes scratches on the paint surface. Under strong sunlight, there are very obvious spider web patterns that affect the car's luster.
Fading: caused by long-term use of the car, resulting in uneven color differences in the car paint.
Water marks, etching marks, cracking: neglecting paint maintenance and not promptly removing surface contamination leads to deep contamination.
2. Determination method: There are two methods for determining, visual and tactile.
(1) Visual
Observe using different light sources, such as natural light, fluorescent lamps, and other artificial light sources, which will help identify paint defects. Paint determination requires a strong light source, such as intense sunlight or sun lamps set at different angles.
(2) Tactile
Observation alone cannot accurately determine defects; using touch can uncover issues that vision cannot detect.
1) Wash your hands and dry them, then touch the paint surface with your palm, especially paying attention to the sensation of your fingers, to discover paint defects. A well-protected paint surface feels like glass. If the paint surface does not feel as smooth as glass, it will be difficult to achieve a good gloss.
2) Cover your fingers with the plastic packaging paper from a cigarette pack and touch the paint surface. This amplifies the roughness of the paint surface. If the paint surface feels very rough, it indicates a more serious oxidation layer.
3. Solution methods
1. Contamination can be handled by washing the car with shampoo or cleaning the paint surface.
2. Deep contamination can be addressed by paint grinding and polishing methods, and more severe cases may require sandpaper grinding.
3. Paint surfaces with stripes or feeling rough when touched with cigarette pack paper need to be ground, polished, and protected with wax.
4. Develop a reasonable car beauty maintenance plan, regularly wash and wax the car.
(II) Analysis of automobile corrosion and dirt
1. Factors affecting automobile corrosion and preventive measures
(1) Reasons for automobile corrosion
1) Dirt or debris containing moisture remaining on parts of the body panels, spaces, or other areas.
2) Damage to the spray-painted layer or other protective layers caused by gravel or minor traffic accidents.
3) Accumulation of sand, dirt, or water under the body.
4) In areas with relatively high humidity (such as coastal areas), corrosion accelerates; in areas where temperatures remain above freezing, atmospheric pollution occurs, and salt is spread on roads, corrosion becomes more severe.
5) High humidity and poor ventilation can accelerate the corrosion of components.
(2) Measures to prevent automobile corrosion
1) Regularly wash the car and wax it periodically to protect the painted layer and maintain brightness.
2) Frequently check the vehicle for small damages and repair them promptly if found.
3) Keep the drainage holes at the bottom of the doors and rear panels clear to avoid water accumulation and prevent corrosion.
4) Regularly inspect the underside of the body and the doors, and if sand or dirt is found, rinse it off with water.
2. Analysis of automobile dirt
(1) The dirt on automobiles and their components includes external deposits, residual lubricants, carbon deposits, rust, soot, and old paint layers. Since these dirt have different properties, the difficulty of removing them from the surface also varies. Dirt often has high adhesion, firmly attaching to the surfaces of components.
1) External deposits
External deposits can be divided into dust, sedimentary deposits, and greasy deposits. The atmosphere often contains a certain amount of dust. Near moving vehicles, when the particle size of the dust is 5-30 millimeters, the dust content reaches about 0.05g/cubic meter. As the dust particle content increases, its condensation and deposition on metal surfaces accelerate. In humid air, due to the adsorbed water film increasing the adhesion between dust particles, the condensation of dust particles accelerates. The degree to which dust particles adhere to the surface depends on the cleanliness of the surface, the size of the dust particles, and the humidity of the air. Greasy deposits form when mud and dust fall onto parts contaminated by engine oil. Conversely, lubricating oil falling onto a contaminated surface can also cause this, with the lubricant penetrating the mud.
2) Lubricant residues
Lubricant residues are the most common type of dirt in engines. During vehicle use, lubricants undergo rapid changes, undergoing an "aging" process of oxidation and polymerization. However, removing lubricant residues from parts that have been working long-term in a lubricant medium is quite difficult.
3) Carbon deposits
Carbon deposits in engines can be classified into: carbon buildup, lacquer-like deposits, and precipitates. Carbon buildup consists of hard carbonized materials that accumulate on engine parts. Lacquer-like deposits form a thin film in the piston ring area and also appear on the piston skirt and inner walls. Precipitates deposit on the cylinder walls, crankshaft necks, gears, oil pumps, filters, and lubrication channels, forming sludge. The main reason for the formation of carbon deposits in engines is the thermal oxidation of hydrocarbons. As the degree of oxidation of lubricants and fuel increases, the quantities of oxygen-containing acids, carbonaceous asphalt, and carbonized materials in the oxidation products also increase.
4) Carbon buildup
The main composition of carbon buildup results from the combustion of fuel and lubricants in high-temperature zones, forming hard, non-sticky carbon particles. In lower temperature regions, the oxidation and concentration changes of lubricants are not very drastic, forming viscous high-molecular compounds. These compounds deposit on parts as a thin layer of paint film, which has the ability to adhere carbon particles from burned fuel and lubricants onto its own surface. The gradual aggregation of these particles constitutes carbonized deposits (carbon buildup). Depending on the structure of the engine, usage conditions, and the nature of the fuel and lubricants used, the chemical composition of carbon buildup varies. In automobile engines, the main components of carbon buildup are: carbonaceous asphalt and carbonized materials (mass fraction of 30%-70%), lubricants and tar (mass fraction of 8%-30%), and the remaining components include oxygen-containing acids and ash. Therefore, carbon buildup mostly consists of insoluble or difficult-to-dissolve components, making it hard to remove.
5) Rust
Rust forms due to the chemical or electrochemical destruction of metals and alloys. It is easy to form a slightly reddish-brown film - hydrated iron oxide (rust) - on the surface of steel parts. Hydrated oxides dissolve in acid but only slightly in alkali and water. Aluminum parts also rust, producing a gray-white film, namely aluminum oxide or hydrated aluminum oxide. When using an engine, scale forms in the cooling system. The scale formed on the walls of the engine coolant jacket and radiator makes heat exchange difficult and disrupts the normal operation of the engine. The dissolved calcium salts and magnesium salts (i.e., water hardness) in water are the conditions for scale formation. Hardness can be divided into temporary (carbonate) and permanent (non-carbonate) types. Calcium bicarbonate, magnesium bicarbonate, and calcium sulfate dissolved in water are called temporary hardness. In addition to scale, mechanical impurities (sand, soil), organic matter (tiny organic matter, plants), and rust falling into the engine cooling system form silt deposits.