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What is surface pretreatment for thermal spraying
Oct 22, 2018

Surface pretreatment of thermal spraying is generally divided into three steps: surface pretreatment, surface purification and surface coarsening (or activation).

1. Surface pre-processing:

One is to make the workpiece surface suitable for coating deposition, increase the bonding area;

Second, it is helpful to overcome the shrinkage stress of the coating.Some parts of the workpiece are preprocessed to disperse the local stress of the coating and increase the shear strength of the coating.The usual method is to cut round corners and precoated groove.The rough thread on the workpiece surface is also one of the commonly used methods, especially in large workpiece spraying, cutting thread is often used to increase the joint area.

2 surface purification:

Solvent cleaning, alkali cleaning and heating degreasing are often used to remove surface oil and maintain cleanliness.Common cleaning solvents are: gasoline, acetone, carbon tetrachloride and triclohexene.Large repair workpieces are often cleaned with lye.Lye is usually prepared with sodium hydroxide or sodium carbonate, which is a cheaper method.

3. Sand blast roughening: this is an important pretreatment method for thermal spraying.

Sandblasting allows a clean surface to form a uniform and uneven rough surface to facilitate the mechanical combination of the coating.Using clean compressed air to drive clean sand to spray on the surface of workpiece can make the substrate surface produce compressive stress, remove the surface oxidation film, and cause lattice distortion of some surface metals, which is conducive to the physical binding of coating.The base metal can obtain clean, rough and highly active surface after sandblasting.

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