Common defects and prevention methods of refurbished painting --- pinholing, eye numbness, bubble

Pinholes, numbness, and bubbles mainly refer to the defects of the paint film after the topcoat is sprayed. Pinholes and bubbles often occur at the same time , that is, after the bubbles occur, they gradually disappear and the paint film shrinks to form pinholes. There are also pinholes that do not generate bubbles after spraying and directly form pinholes when the paint film shrinks. Pockmarks mainly occur in the putty part, forming small flake pockmarks, which are mainly caused by insufficient scraping of the putty.

1. Causes

Moisture is mixed in the paint or thinner, which is easy to produce pinholes after spraying.

Oil stains and moisture on the surface of the base layer before painting have not been effectively removed.

The local paint film is sprayed too thick and the solvent in the paint evaporates rapidly to push up the skin and generate bubbles. (Related instrument: Coating Thickness Gauge)

The two-component paint equipment is not clean, if there are water stains, oil stains, acid and alkali impurities, resulting in pinholes or pitting.

The compressed air used for spraying is not clean, for example, contains water, oil, etc., causing air bubbles and pinholes.

When spraying polyurethane paint, it is easy to produce pinholes or numbness if it is sprayed too thick.

Poor scraping of putty (mainly refers to flatness) is prone to numbness.

2. Preventive measures

Thinners should be used in a standard manner and should not be used indiscriminately.

Before each spraying, wipe with paper or hand to check whether the compressed air is clean, if there are impurities, stop using it.

Spraying tools and containers should be kept clean and free from impurities such as water and oil.

When spraying two-component paint such as polyurethane, it should be careful not to be too thick, and the surface should be dry and clean before spraying.

When spraying and renovating outdoors, avoid sun exposure to prevent air bubbles or pinholes.

The surface after lightening is pockmarked, and it needs to be cleaned out repeatedly with pockmarking ash.