Investment castings often require mid-term rust prevention. Rust prevention methods generally use rust prevention liquid treatment or oil seals. Castings must be cleaned before rust prevention.
Casting cleaning
The formula, temperature and use of commonly used cleaning liquids are as follows. After washing, the castings must be blown dry with dry compressed air.
Acidic cleaning liquid formula and use
| No. | Formula (mass fraction,%) | Time/ min |
Application | ||||
| hydrochloric acid | Hydrofluoric acid | Nitric Acid | Water | Corrosion inhibitor (external) | |||
| 1 | 20 | 10 | / | 70 | Moderate | 2-10 | Carbon steel castings low alloy steel castings |
| 2 | 20 | 10 | 10 | 60 | Moderate | 5-10 | Stainless steel castings |
Water-based cleaning liquid formulation, temperature and use
| Detergent composition and content (mass fraction, %) | Washing liquid temperature/℃ | Application | ||||
| Potassium dichromate | Na2CO3/Na3PO4 | Water glass | Glycerin | Water | ||
| 0.1-0.2 | 0.15-0.25 | 0.15-0.3 | / | Moderate | 75-90 | Copper alloy castings steel castings |
| / | 0.1-0.2 | 0.35-5 | 3.5-5 | Moderate | 75-90 | Copper alloy castings steel castings |
| 0.5-1 | 1.5-2.5 | 1.5-3 | / | Moderate | 50-60 | Aluminum alloy castings |
Anti-rust treatment
When using rust removal liquid, the ingredients of the commonly used anti-rust liquid are as follows:
| No. | Formula (mass fraction,%) | Application | ||||||
| NaNO2 | Anhydrous Na2CO3 | Sodium benzoate | Triethanolamine | Potassium dichromate | CrO3 | K2CrO4 | ||
| 1 | 20 | / | 5 | 0.6 | / | / | / | Steel Castings |
| 2 | 15-20 | 0.5-0.6 | / | / | / | / | / | |
| 3 | / | / | / | / | 30 | 1 | / | Copper alloy castings |
| 4 | / | / | / | / | / | / | 2 | Aluminum alloy castings |
Among them, No. 4 anti-rust liquid is the most commonly used one for steel castings. The more NaNO₂ content in the anti-rust liquid, the stronger its anti-rust ability, otherwise the weaker its anti-rust ability. During the treatment, after the casting is cleaned and dried, the casting is immersed in the anti-rust liquid, and it can be taken out after keeping it for 1-3 minutes.
Oil seal
There are two main methods for casting oil sealing: cold coating method and hot coating method.
1. Cold oil coating method
The cold oil coating process is feeding (putting the casting into the hanging basket) - washing (120 or 200 solvent gasoline) - drying (50-60 ℃ hot air) - oiling (anti-rust grease) - packaging.
2. Hot oil coating method
The hot oil sealing dipping process uses kerosene or gasoline as a cleaning agent for cleaning; neutral industrial vaseline or aviation lubricating oil plus refined wax with a mass fraction of 4%-6% as anti-rust grease is dipped twice. The first dipping is 5-20 minutes at a temperature of 110-120 °C; the second dipping is about 5 minutes at a temperature of 60-70 °C.
Post time: Feb-08-2025