How to determine the quality of phosphate film before painting?

After phosphate, according to its use, its quality index is itemized. The main quality control indicators, including phosphate membrane appearance, phosphate film thickness or film weight, phosphation film or after treatment corrosion resistance three common indicators. According to phosphate use sometimes also have to detect: phosphate and paint film matching, phosphate film hardness, coefficient of friction, anti-scratch and other indicators
China
. With regard to the three common indicators of phosphate, the following criteria and methods can be referred to.Phosphate membrane appearance:
using visual inspection, the relevant standards
GB 11376-89
"Metal phosphate conversion film" and
GB 6807-2001
"Steel work parts before painting phosphate treatment technical conditions."phosphate film thickness or film weight:
film thickness measurement using
GB 6462
metal oxidation mulden cross-section thickness microscope measurement method, can also be used thickness gauge, according to
GB 4956
"Magnetic method for measuring non-magnetic mulden thickness on magnetic metal substates" or
GB 4957
"Non-conductive covering on non-magnetic metal substations to measure eddy currents". The weight method for film weight measurement can be determined in accordance with
GB 6807
Technical Conditions for Phosphate Treatment before painting steel work pieces or
GB 9792
the quality of the upper layer of the conversion film unit area on metal materials.corrosion resistance:
detection of corrosion resistance of the phosphate film itself can be using copper sulfate drop method, sodium chloride salt water immersion method and salt spray test method. Dotting method and salt water immersion method can be in accordance with
6807-2001
"Steel parts before painting phosphate treatment technical conditions", phosphate film after treatment such as oil, wax, paint after the general salt spray test. The salt mist test may be carried out in accordance with
GB 1771-79
Paint Film Salt Resistance Salt Mist Assay or
GB 6458
Metal Cover Neutral Salt Mist Test.
1
, pre-paint bottoming with phosphatefor the phosphate treatment of pre-paint bottoming, the main purpose is to improve the adhesion of the paint film and coating system corrosion resistance, so the focus is on the performance of the paint film. General phosphate quality test indicators include membrane appearance, film thickness and the performance of the paint film. The appearance of the film should be uniform fine and complete phosphate film, the appearance of the light iron system phosphate, its appearance should be uniform fine and complete phosphate film, the appearance of the light iron system phosphate, its appearance should be a complete red and blue color film. Phosphate film should not be too thick, the general film weight should be less than
7.5g/m
2
,
best for
1.5
to
3.0g/m
2
, for light iron phosphate film weight
0.5
to
1.0g/m2
is appropriate, too thick and rough phosphate film is unfavorable. Corrosion resistance indicators include corrosion resistance of the phosphate film itself and yellowing rust should not occur before painting. The corrosion resistance after phosphate and paint is the most important, it reflects the overall corrosion resistance after phosphate film and paint. In addition to detecting corrosion resistance after phosphate film and paint, it is generally necessary to determine the mechanical and physical properties of its paint film, such as: adhesion, impact strength, bending resistance (flexibility) and so on.quality index and testing method of phosphate before painting should generally refer to the national standard
GB 6807-2001
"Technical conditions for phosphate treatment before painting steel work pieces", which on the quality of phosphate film Indicators and testing and evaluation methods have more detailed provisions, the main contents are as follows:(
1
) phosphate film appearance should be crystalline dense, continuous uniform light gray to dark gray film, for light iron phosphate should be continuous color film. The following defects are permitted, such as slight water traces, chromate traces, mild ash hanging, phosphate membrane defects due to different surface states such as heat treatment welding and processing. For the following are not allowed defects: yellowing rust in phosphate film, loose phosphate film, phosphate dew bottom local membraneless, serious hanging ash.(
2
) paint with phosphate film weight should be less than
7.5
g
/m
2
.(
3
) corrosion resistance of phosphate film using salt water immersion method, phosphorus chemical parts in
3% NaCl
aqueous solution, in
15
to
25
degrees C
temperature, soaking
1h
should not appear rust. Corrosion resistance test after phosphate and paint film is the phosphorus chemical parts coated
25
to
35 m

A04-9
white ammonia paint, after scratching salt spray test (According to
GB 1771-79
) by
24h
salt mist test (iron phosphate is
8h
salmite fog test) paint film should be free of foaming, rusting, shedding phenomenon.
GB 6807-2001
copper sulfate drop method is not considered as a necessary test item, considered to be a rapid test of the quality of phosphate between processes, and phosphate and paint after corrosion resistance as a mandatory item.test indicators and methods for pre-paint phosphation can also be referred to
GB 11376-89
Metal Phosphate Conversion Film.
Therefore, from the standard provisions of the inspection project, the pre-paint bottoming phosphate should be dense, uniform, thin layer phosphate film, should focus on testing phosphate and paint after corrosion resistance and mechanical physical properties.2 anti-rust, corrosion-resistant phosphatefor this type of phosphation, the main purpose is corrosion protection, its corrosion resistance is the most important indicator. The general quality test index copper drops of sulphate are greater than
1min
, salt-resistant water is greater than
2h
, and the salt spray test is greater than
1.5h
. For corrosion resistance testing after oil or waxing, it is best to use salt spray test, the specific salt spray resistance time should be reached, can be agreed by both supply and demand.
3
,
lubrication, wear-resistant mophosphatelubrication action of phosphation is mainly used in cold processing, generally zinc system. Wear-resistant mophosphation is a workman for load friction movement, and manganese phosphation is common. for lubrication phosphate, the main test appearance, film weight, corrosion resistance and smoothness after saponification, and sometimes to determine the coefficient of friction. It is required that the appearance of phosphate film should be uniform and complete, the general film is significant in
5g/m2,
to ensure that there is a certain film thickness, after soaping, significantly reduce friction, reduce mold damage, reduce cracking when the work parts are cold. for wear-resistant mophosphate, generally manganese phosphate, the appearance of its phosphate film should be uniform complete deep ash or black film. For components with small clearance, the film weight should be
1
to
3g/m2
, and the film weight should be more than
5g/m2
for work parts with large clearance. This type of phosphate is required to have a high hardness and anti-scratch performance, the specific indicators can be agreed by both supply and demand. At the same time, wear-resistant phosphate should have better corrosion resistance, usually salt-resistant fog should be more than 1.5h
1.5h
. For lubrication, wear-resistant and phosphorus reduction can also be
GB 1176-89
.


phosphating
phosphating for 4 and
other purposes can be used in addition to the above three fields, but also for electrical insulation, decorative aspects. Its general quality detection indicators are appearance, film weight and corrosion resistance. For electrically insulated phosphating, the surface resistance on the unit area is required to be detected. Decorative phosphate should be dyed according to different requirements, requiring different color colors and corrosion resistance, these indicators of detection methods and control range is generally agreed by both supply and demand.
phosphate quality index detection and control, according to its use of different requirements, in addition to the conventional appearance, film weight, some phosphate corrosion resistance standards can be followed, most of the indicators and testing methods are agreed by both supply and demand.