Rust after phosphating

After reading your phosphating process, it should be iron phosphating. The antirust performance of iron-based phosphating film itself is not as good as that of zinc-based phosphating, mainly because the iron-based phosphating film is relatively thin. You only have four tanks, so it is difficult to achieve high-quality iron-based phosphating film.

From the process flow, the original oil removal and rust removal are combined (without heating), and the oil stain cannot be removed when it is heavy, and it will rust after phosphating. Even if it is later changed to alkaline degreasing, the oil stain cannot be removed because there is no heating, and it will rust after phosphating.

Is your iron-based phosphating film rainbow (color film)? Rainbow phosphating film, to put it bluntly, is caused by the low content of sodium molybdate in phosphating solution (mainly to reduce costs). If you can get a blue phosphating film, it should not rust after a few days. This is a high-quality iron phosphating film.

High-quality iron phosphating must be washed, and the phosphating film that can not be washed or washed on the surface can not meet the requirements of national standards.

Solution:

1. Improve your phosphating process (heating, adding bath, adding water).

2. Replace the existing phosphating solution and choose a phosphating solution with good quality.