Metalwork parts are prone to rusting during manufacturing, processing, and transportation. Rust is formed when oxygen and moisture react with the metal surface, causing electrochemical corrosion that produces a mixture of oxides and hydroxides. Iron rust is reddish, copper rust is green, and the rust on aluminum and zinc is known as white rust. To prevent corrosion, anti-rust products must block contact between these corrosive agents and the metal; anti-rust inhibitors are a type of such product. In manufacturing and processing, water-based anti-rust inhibitors and anti-rust oils are commonly used.

Regarding the use and daily maintenance of rust inhibitors, as well as strategies for addressing common issues, our LORD Chemical engineers would like to offer the following key recommendations:

Before use:

1. Cleaning the Rust-Prevention Tank: Before switching to a different type of rust inhibitor, or after the product has been in use for a certain period, it is essential to thoroughly remove all residual solution from the tank prior to preparing and adding the new solution. Failure to clean the tank properly before adding the new solution will compromise the rust-inhibiting performance of the agent and shorten its service life.

II. Water Quality Inspection: The quality of the water used to prepare the rust-inhibitor working solution is critically important; treated deionized water should be used whenever possible (deionized water conductivity < 10 μS/cm). If deionized water is not available, tap water may be used, but the formulation concentration must be at least doubled.

3. Proper Preparation of Rust Inhibitor: Before use, determine the dilution ratio and the required amount of rust inhibitor. Next, calculate the volumes of the undiluted rust inhibitor and water needed, add the required amount of water to the rust-inhibition tank, and then add the undiluted rust inhibitor.

For the determination of rust inhibitor concentration, different types of rust inhibitors have different refractive indices and calculation formulas. For technical inquiries, please call: 400-806-1006.

In use:

Maintenance and management of rust inhibitors: primarily involve two aspects—preventing the ingress of external contaminants and promptly removing any that do enter, and maintaining stable concentration and temperature of the rust inhibitor.

1. Maintain Cleanliness: In general, external contamination of the rust-prevention bath originates from impurities carried over from preceding process steps. During routine production, it is essential to install a rinsing tank upstream of the rust-prevention bath and to maintain overflow in the rinsing tank as much as possible, thereby minimizing the ingress of impurities into the rust-prevention bath.

II. Regular Monitoring: Establish a dedicated record-keeping system for the management of rust inhibitors. Conduct daily scheduled checks of concentration and temperature, and maintain accurate records of the relevant data. Operating procedures shall be developed. When the concentration or temperature of the rust inhibitor deviates from the normal range, corrective measures shall be implemented promptly. Relevant training shall be provided to operators.

3. Regular Replacement: Since rust inhibitors are inevitably contaminated during use, which can compromise their performance, it is essential to establish a practical and feasible schedule for regular replacement based on actual production conditions. In addition, if any of the following conditions are observed during operation, prompt replacement with fresh inhibitor should be considered, followed by thorough cleaning of the rust-prevention tank and related equipment: discoloration or unusual odor in the working solution; a sudden and significant drop in inhibitor concentration as monitored; or widespread, short-term rusting of the workpieces. In such cases, the working solution should be appropriately adjusted, filtered, or replaced as necessary.

Frequently Asked Questions and Corresponding Solutions:

1. The part surfaces are clean, but rust develops rapidly after the cleaning and rust-prevention process: this may be due to the presence of “rust nuclei” on the parts prior to cleaning (i.e., microscopic rust that is not visible to the naked eye but can be observed with a magnifying glass). Therefore, management of parts before cleaning should be strengthened.

II. The rust-prevention period shortens after parts are stored for a period of time:

① Possible causes include excessively high relative humidity in the warehouse and malfunctioning dehumidification equipment: In this case, the relative humidity should be monitored and maintained at or below 55%.

② Occurs during seasons characterized by humid and muggy weather, when ambient relative humidity is high: Under these conditions, the concentration of cleaning and rust-prevention solutions should be appropriately increased, and the turnaround time for parts should be accelerated to reduce dwell times in each process step.

③ Inadequate rust prevention during outsourced rough machining: Outsourced manufacturers are required to implement effective rust-prevention measures for parts; season-specific rust-protection deadlines must be communicated to these manufacturers, and delivered semi-finished products must be inspected upon receipt to verify that no rust has formed.