How to reduce the loss of protective coatings during the coating process.

If you can minimize the loss of protective coatings during the coating process, you can maximize the use of protective coatings, thereby reducing the cost of coating protective coatings.
to understand the loss factor before discussing how to reduce the loss of protective coatings.
loss factor (loss factor), that is, the difference between the theoretical coating rate and the actual coating rate, which is expressed as a percentage of the theoretical coating rate

. That is:
loss factor cannot exceed 100%. The coefficients we often use to calculate (e.g. 1.8) should not be called loss coefficients, we can call them "calculation coefficients". Relationship between the two: the calculation coefficient is 1 / (1 -loss factor) e.g. the loss coefficient is 45%, then the calculation coefficient is 1/0.55 x 1.818.
the composition and influence factors of surface loss
1, loss caused by surface roughness
because the surface of steel structure treated by surface rust removal has a certain roughness (for most anti-corrosion structures, roughness value RY5 is generally For 40-90 microns, or ISO8501-1 in the G grade, the rugged surface has a larger surface area than the plane, resulting in coating losses related to surface roughness and coating thickness, generally 3-10%.
2, coating film distribution caused by the loss - the biggest factor
on the one hand, the requirements of the paint film thickness is completely uniform is impossible to achieve, in accordance with the 90-10 or 80-20 paint film thickness control principle to accept the dry film thickness, the average dry film thickness will usually exceed the design of the dry film thickness, which will cause more consumption of paint, on the other hand, in some difficult parts of the construction, excessive coating (super-thick) is more inevitable, will also increase the consumption of paint. Due to the loss caused by coating distribution, roller brushes are usually between 5% and 15%-15%, and spraying is usually 15%-40%.
3, construction losses
and construction methods, component shape and other related, such as spraying paint fog flying, overs spraying, etc. , airless spray construction, this is generally in the range of 5%-60%. Large area structure than small rod parts of the loss is small, when the wind outside construction will also increase this part of the loss.
4, paint waste
paint waste includes: packaging barrel residue, coating equipment adhesion (such as pump and line loss, roller and brush residue, etc.), improper ingredients loss. This part can be considered at 3%-10%.
5, common other factors of actual dosing deviation
1) paint manufacturers for estimated dosing data (volume solids and proportions) are not true! 2) The dry film thickness of the design is not enough to cover, especially some lead-free paint, the cover force is relatively poor; 3) the pre-painting, repair and rework work is too large; 4) the construction operation proficiency is poor, the film thickness control is too uneven or super thick; 5) the area Accounting error; 6) membrane thickness test method (standard), instrument type and accuracy, test error, acceptance criteria followed; 7) wear consumption during construction; 8) substrate porous, such as zinc silicate primer surface, thermal spray metal surface, etc.
Experienced loss factor
in general, the experience loss coefficient is shown below table (the actual situation is recommended floating ±10%):
coating theory dosage estimation
coating theory coating rate and theoretical dosage are inverted, below is the coating theory The calculation formula for the amount
For a certain area of steel structure, taking into account the loss factor, the dosage can be estimated by the following type:
as far as possible to make the coating evenly distributed, pay attention to spraying techniques, at any time to measure the thickness of the wet film and adjust accordingly
to avoid rough over the high.
nozzles with different spray frames according to the shape of the coated steel structure, and nozzles with different flow according to thickness requirements. Avoid habitual dilution and adjust the total output fluid pressure to reduce the cost of thinners. Avoid overspouting. Avoid construction on windy days.
source: Sago Special
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