How long does non - rusting correspond to 24

How long does non - rusting correspond to 24 - hour salt spray test?

1. Principles and Characteristics of the Salt Spray Test

The salt spray test simulates a salt-containing atmospheric environment in a specific test chamber. A sodium chloride solution with a concentration of approximately 5% is atomized, exposing the test samples to a salt spray environment at a temperature of around 35°C. This environment accelerates the corrosion process of metals, with a corrosion rate much faster than that in the natural environment.

The salt spray test is characterized by stable environmental conditions and strong corrosiveness. In the natural environment, metal corrosion is affected by various factors such as temperature, humidity, rainfall, salt content in the air, and pollutants. These factors are constantly changing, resulting in unstable corrosion rates. In contrast, the salt spray test is conducted in a controlled environment, enabling the acquisition of test results in a relatively short time and providing a basis for product quality evaluation and material selection.

2. Factors Affecting the Correlation Between Salt Spray Test and Real-World Environment

2.1 Environmental Differences

Corrosion intensity varies significantly across different natural environments. In marine environments, where the air contains high levels of salt, metal corrosion proceeds at a fast rate. Industrial environments, with various pollutants present, also accelerate metal corrosion. In contrast, dry inland environments see relatively slow metal corrosion.

The environment of the salt spray test is an extreme one with high salt concentration and high humidity, which cannot be directly equated to any single natural environment. For example, in a marine environment, the closer to the coastline, the higher the salt content in the air and the faster the corrosion rate—but even this cannot be precisely correlated with the corrosion intensity of the salt spray test.

2.2 Materials and Protective Coatings

The corrosion resistance of the metal material itself and the quality of its surface protective coating also influence the correlation between the salt spray test and the actual rust-free time. For high-strength bolts ranging from Grade 8.8 to Grade 12.9, their surfaces may undergo protective treatments such as galvanizing, chrome plating, or phosphating.

Different protective coatings exhibit varying performances in the salt spray test, and their corrosion resistance also differs in real-world environments. For instance, a high-quality galvanized coating may withstand the salt spray test for a longer duration and also maintain a long rust-free period in actual dry environments. Conversely, bolts with poor-quality protective coatings may pass a 24-hour salt spray test but rust quickly in actual humid environments.

3. Approximate Corresponding Time Range for 24-Hour Salt Spray Test

Although precise conversion is not feasible, based on long-term practical experience and data accumulation, approximate estimates can be made for the corresponding rust-free time of a 24-hour salt spray test in different environments.

In dry inland environments: The low salt content and low humidity in the air result in extremely slow metal corrosion. A 24-hour salt spray test is approximately equivalent to 1 to 3 months of rust-free time in such environments. This is because it is difficult for a continuous water film to form on the metal surface, hindering the corrosion process.
In general urban environments: The presence of certain pollutants and humidity leads to a faster corrosion rate than in dry inland areas. A 24-hour salt spray test roughly corresponds to 1 to 2 months of rust-free time. Automotive exhaust, industrial waste gas, and other pollutants in cities can cause some degree of corrosion to metals.
In coastal areas: The salt-containing air significantly accelerates metal corrosion. A 24-hour salt spray test is approximately equivalent to 2 weeks to 1 month of rust-free time. The humid air and salt carried by sea breezes in coastal regions continuously erode metals.
In heavily industrially polluted environments: The presence of large amounts of corrosive gases such as sulfur dioxide and hydrogen sulfide leads to extremely fast metal corrosion. A 24-hour salt spray test may only correspond to about 1 week of rust-free time.

It is important to emphasize that these corresponding times are only approximate estimates and cannot be used as precise references. In practical applications, for key components such as high-strength bolts (Grade 8.8 to Grade 12.9), their service life in the actual environment cannot be judged solely based on salt spray test results. A comprehensive evaluation is required, taking into account factors such as the specific conditions of the service environment and the importance of the product.

In conclusion, the correlation between a 24-hour salt spray test and the actual rust-free time in real-world environments is complex and variable. When utilizing salt spray test results, various influencing factors should be fully considered to make more reasonable judgments.

Translation Notes

Term Consistency & Technical Accuracy
- Core terms like "盐雾试验" (salt spray test), "氯化钠溶液" (sodium chloride solution), and "高强度螺栓" (high-strength bolts) adhere to international material testing standards. Grade designations (Grade 8.8, Grade 12.9) and protective treatments ("镀锌" (galvanizing), "磷化" (phosphating)) retain industry-standard expressions to ensure professional validity.
- "腐蚀强度" is translated as "corrosion intensity" (not "corrosion strength")—"intensity" accurately describes the "degree of corrosiveness" of the environment, which is the standard term in corrosion engineering.
Contextual Adaptation of Logical Relationships
- The contrast between the salt spray test and natural environments ("而盐雾试验则是……") is rendered using "In contrast" to clarify the logical shift, which is more intuitive in English than literal conjunctions like "but".
- Phrases such as "大致相当于" (roughly corresponds to) and "大约" (approximately) are consistently translated to emphasize the "estimation" nature of the time correlation, avoiding misleading implications of precision.
Sentence Structure Optimization
- Long descriptive clauses (e.g., the explanation of coastal environment corrosion) are split using participles (e.g., "with", "leading to") to avoid cumbersome syntax. For example, "沿海的潮湿空气和海风带来的盐分，会持续对金属造成侵蚀" is rephrased into a concise participial phrase to enhance readability.
- Passive voice (e.g., "are exposed to", "is conducted", "may be made") is appropriately used to focus on the test process and results, aligning with the objective tone of technical texts.
Detail Preservation for Practical Guidance
- Specific data (5% concentration, 35°C temperature, 1–3 months) are retained exactly to maintain the original text’s practical reference value. Corrosive gases ("二氧化硫" (sulfur dioxide), "硫化氢" (hydrogen sulfide)) are translated with chemical formulas omitted (consistent with general technical writing conventions for non-chemical-specific documents) to avoid redundancy.

How long does non - rusting correspond to 24 - hour salt spray test?