Some standard content:
Guiding Technical Documents of the Sixth Machinery Industry Department of the People's Republic of China
Technical Conditions for Phosphating of Ferrous Metals
CB/Z94-68
1. This document is applicable to the phosphating treatment of ferrous metals - hull steel plates, ship accessories and various mechanical parts. 2. After the parts of the above materials are phosphated, a perfect phosphating film is formed on the surface of the parts. The phosphating film, as the bottom layer of the paint, can significantly improve the adhesion between the paint film and the base metal; improve the rust resistance of the materials and parts. If the surface is immersed in oil, the rust resistance of the parts can be further enhanced.
3. After phosphating, the friction coefficient between the two friction pairs of mechanical friction parts can be significantly reduced. The appearance of the phosphating film is light gray, gray-brown (special alloy material) with a slight brown, and there are grains visible to the naked eye in the sun. 4.
Characteristics of phosphating film: poor mechanical strength, not resistant to friction, brittle and not allowed to be bent. II. Phosphating Specifications
The main component of the phosphating solution is Marif salt, which is a white or slightly reddish crystalline powder solid. When preparing the phosphating solution, Marif salt is dissolved in boiling water, boiled for 2 hours, and then cooled to precipitate the precipitate. Before using the phosphating solution, it must be preheated to hydrolyze the iron phosphate and manganese phosphate. When the parts are immersed in the phosphating solution, the iron ions in the solution increase and a large amount of gas is precipitated. At this time, the phosphate radicals in the solution and the metal ions form insoluble compounds that are deposited on the surface of the parts and crystallize into a phosphating film. The phosphating specifications are set as follows: (1) Ordinary carbon steel.
Marif salt
Total acidity
Free acidity
Total acidity
Free acidity
Temperature()
Time (min)
(Until the bubbles around the parts stop precipitating) (2) Chromium, molybdenum, manganese, silicon alloy steel.
Mariv salt
Total acidity
Free acid
Temperature (℃)
Time (min)
(Until bubbles around the parts stop precipitating)
(3) Alloy cast iron.
Mariv salt
Total acidity
Published by the Sixth Ministry of Machinery Industry
30~35 g/L
28~32 (titer)
4~5 (titer)
96~100
30~40 g/L
30~42 (titer)
4~7 (titer)
9 8~110
30~35 g/L
36~38 (titer)
Approved on July 1, 1968
Total 6 pages Page 2
Free acid
Temperature (℃)
Time (min)
CB/Z94-68
(Until bubbles around the parts stop precipitating) (4) Rapid phosphating.
Mariv salt
Zinc nitrate
Total acidity
Free acid
Temperature (℃)
Time (min)
(5) Cold phosphating.
Mariv salt
Zinc nitrate
Zinc oxide
Sodium nitrate
Total acidity
Free acid
Temperature (℃)
5~6 titer)
96~100
30~35 g/L
25~30 g/L
40~50 (titer)
2.5~5.5 (titer)
44 g /L
1.5g/L
~10g/K
30~35g/L
60~80g/L
8~15g/L
4~5g/L
1g/K
40~60 (titer)
0.8~1.9 (titer)
(After the bubbles around the parts stop precipitating, keep it for about 20 minutes) (6) Cold phosphating.
Mariv salt
Zinc nitrate
Sodium fluoride
Zinc oxide
Total acidity
Free acid
Total acidity
Free acidity
Temperature (℃)
Time (min)
(7) Phosphating of zinc nitrate at medium temperature.
Mariv salt
Zinc nitrate
Zinc oxide
Sodium fluoride
Temperature (℃)
Time (min)
64 g/K
80 g/L
6 g/L
8 g/K
70~72 (titer)
28~30 (titer)
60 g/L
60 g/L
7 g/K
3 g/K
Note: ① Regarding marine plates, there are no rigid regulations for the phosphating specifications of the accessories. The above specifications can be selected and treated separately by each factory according to different product technical requirements.
CB/Z94-68
III. Main Technical Conditions
Total 6 pages Page 3
The preparation process before phosphating of steel parts is generally carried out according to the requirements of the parts themselves and the original surface oxide scale rust situation according to the following two schemes.
Scheme 1:
For rough parts, no tolerance finish requirements, and serious rust oxide scale on the surface; the thickness of the parts themselves is greater than 2 mm, shot blasting can be carried out, and sand blasting is also allowed in a sealed room or sealed cabinet, and then phosphating. Second option:
Chemical cleaning (including phosphating process step) steps:
(1) Remove seal, chemical degreasing;
(2) Hot water cleaning;
(3) Cold water cleaning;
(4) Pickling;
(5) Cold water cleaning: Www.bzxZ.net
(6) Neutralization and soap solution;
7. Chemical degreasing regulations.
Sodium hydroxide (NaOH)
Sodium carbonate (NazCO,)
Sodium silicate (Na,SiO,)
Temperature (℃)
8. Pickling regulations.
Industrial sulfuric acid (H2SO4)
Ferrous sulfate (FeSO4)
Temperature (℃)
Industrial sulfuric acid (HSO4)
Industrial hydrochloric acid (HCI)
Temperature (℃)
(7) Phosphating (according to any previous formula);
(8) Hot water cleaning;
(9) Drying;
(10) Dichromate treatment;
(11) Inspection,
(12) Supplementary treatment.
80~120g/L
45~50g/L
5~10g/L
96~100
Until the oil stains are completely removed
10~15% (volume ratio)
1~1.5g/L
<150g/L
Until the rust and scale are completely removed
10% (volume ratio)
15% (volume ratio)
1.5~3g/L
Until the rust and scale are completely removed
Note: ② For precision-machined parts with tolerance requirements, try not to perform acid etching, or use H,SO.3-5% acid solution for weak etching instead. 9. Neutralization and soap solution requirements.
Sodium carbonate (NazCO,)
Temperature (℃)
Time (min)
Note: ③ For parts with tolerance requirements, clean with cold water and dry with compressed air, then wipe the surface to be phosphated with aviation lubricating oil or glycerin with clean gauze to make a thin oil film on the surface of the part (to improve the formation of the initial phosphating film of the part to prevent excessive corrosion) and then directly carry out phosphating. 10. Dichromate treatment regulations.
Sodium dichromate (Na2Cr2O))
Temperature (℃)
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Time (seconds)
11. Supplementary treatment regulations.
Aviation oil, or spindle oil
Temperature (C)
Time (min)
Apply a layer of protective dry oil
Dry oil (linseed oil or catalpa oil)
Gasoline or rosin water
12. Adjustment of phosphating solution.
CB/Z94-68
100~110
The acidity of phosphating solution must meet the process specifications. If the acidity of the solution is low, it can be adjusted with Marif salt or dihydrogen manganese phosphate. On the contrary, if the acidity of the solution is too high, it can be adjusted with manganese carbonate or zinc oxide. The adjustment work can be carried out directly in the phosphating tank. For this purpose, the solution should be heated to about 80°C. The adjusted solution should be clarified before phosphating. 13.The analysis of phosphating solution is as specified in Table 1. Table 1
Total acidity
Free acidity
Mn,Fe,Zn
Pb,Al,Cu
14. Insulation of non-phosphating surface.
(g/K)
10% deviation from standard
10% deviation from standard
Mn=10-13
Mn41g/L,Fe>1.6g/L
Very small amount of acid radical
In order to ensure that no phosphating film is produced on the non-phosphating surface, appropriate insulating coating must be applied before phosphating. The insulating material is polystyrene. During preparation, xylene is used as solvent and ethyl acetate is added appropriately. The formula is as follows: Polystyrene
Xylene
Ethyl acetate
Preparation process: First weigh xylene, then add the required amount of polystyrene and stir to mix evenly, and finally add ethyl acetate. It can be used only after the polystyrene is completely dissolved. If the viscosity is too high during use, ethyl acetate can be added appropriately to dilute it. Insulation work should be carried out 1 hour before phosphating to allow the insulation layer to be completely dry. IV. Acceptance rules and methods
15. The quality acceptance of phosphating film must comply with the following specified acceptance items, among which the quality requirements of hull steel plates and accessories only need to meet the requirements of (1) and (4) for acceptance.
(1) Appearance inspection. After phosphating, the parts should first meet the requirements of appearance quality inspection, and then other performance inspections can be carried out. It can be observed under natural light during the day and at night at a distance of 300 to 400 mm and 100 watt light. The phosphate coating should be complete, with an appearance of gray, dark gray or black, and the following conditions are allowed: a
Brown-black color caused by different steel grades
A few small spots and not serious white gray;
CB/Z94-68
Slight wear on the edges and corners of the fixture contact area; corrosion before phosphating and places that are difficult to blast with sand present patterns or unevenness; different metal structures after different heat treatments cause inconsistent colors; steel products with high content of chromium, manganese, silicon, vanadium, tungsten and other elements present patterns or different colors, and the phosphate layer is not obtained at the welding place with special welding rods. The following conditions are not allowed for the phosphate coating:
The base metal is exposed due to incomplete phosphating;
Serious spots and grains are significantly uneven; the base material of the parts is obviously corroded;
Yellow rust marks appear after washing with hot water.
(2) Wear resistance. Painted parts can be exempted from this requirement. If the surface is exposed to the outside after phosphating and is often in contact with friction, this inspection should be carried out. Inspection method: Use a white cloth dipped in spindle oil to manually wipe the phosphating film for 1 to 3 minutes. The surface of the white cloth is not allowed to be blackened. The number of random inspections is 1% of each batch of parts.
(3) Phosphating film thickness. 3 to 5% of mechanical parts that are finely processed and have matching requirements are randomly selected for phosphating film thickness inspection. General parts do not need to be inspected. Inspection methods can be measured by measuring tools and metallographic sectioning methods. The thickness of the phosphating film can be classified into the following two categories: Mechanical parts
Hull steel plates, accessories
5 to 30 microns
30 to 80 microns
Matching parts, due to tolerance requirements, if there is a size deviation, but the situation is not too serious, it is allowed to be appropriately ground and corrected.
(4) Corrosion resistance.
The inspection of the corrosion resistance of the phosphate film is carried out before oil immersion or paint immersion. The inspection quantity is 1~3% of each batch of parts (it is allowed to be measured with corresponding samples).
Inspection method:
a. Salt water corrosion.
Put the phosphated parts or samples (which have been cooled to room temperature) in a 3% sodium chloride (NaCl) solution and immerse them for 2 hours at room temperature. No rust spots are allowed.
b. Drip method
Test solution composition:
0.1N hydrochloric acid (HC1, 1.19)
0.4N copper sulfate (CuSO.·5H2O)
10% sodium chloride (NaC1)
0.8 ml
40 ml
20 ml
Use a pipette to drop the above solution on the surface to be measured, and observe the color change according to the stopwatch or watch second hand, from the initial azure to yellow or red.
Quality assessment is determined according to the time of color conversion and is divided into four levels according to Table 2. The quality acceptance of parts is based on categories 1, 2, and 4 as the qualified standards. (5) Process inspection.
In addition to the above requirements, strict process inspection must be carried out to ensure product quality, including operating procedures, operating temperature, phosphating end time, total acidity and free acidity of the phosphating solution. Total 6 pages Page 6
Conversion time
CB/Z94-68
Protective capacity and other
Cold phosphating19)
0.4N copper sulfate (CuSO.·5H2O)
10% sodium chloride (NaCl)
0.8 ml
40 ml
20 ml
Use a pipette to drop the above solution on the surface to be measured, and observe the color change from the initial azure to yellow or red according to the stopwatch or watch second hand.
Quality assessment is determined according to the time of color conversion and is divided into four levels according to Table 2. The quality acceptance of parts is based on categories 1, 2, and 4 as the qualified standards. (5) Process inspection.
In addition to the above requirements, strict process inspection must be carried out to ensure product quality, including operating procedures, operating temperature, phosphating end time, total acidity and free acidity of phosphating solution. Total 6 pages Page 6
Conversion time
CB/Z94-68
Protective capacity and other
Cold phosphating19)
0.4N copper sulfate (CuSO.·5H2O)
10% sodium chloride (NaCl)
0.8 ml
40 ml
20 ml
Use a pipette to drop the above solution on the surface to be measured, and observe the color change from the initial azure to yellow or red according to the stopwatch or watch second hand.
Quality assessment is determined according to the time of color conversion and is divided into four levels according to Table 2. The quality acceptance of parts is based on categories 1, 2, and 4 as the qualified standards. (5) Process inspection.
In addition to the above requirements, strict process inspection must be carried out to ensure product quality, including operating procedures, operating temperature, phosphating end time, total acidity and free acidity of phosphating solution. Total 6 pages Page 6
Conversion time
CB/Z94-68
Protective capacity and other
Cold phosphating
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