FAQ

Today, a customer gave feedback:

Acidic rust remover reacts with rust-proof oil. Is there a better rust remover alternative?

Background: The factory manufactures fuel tanks and hydraulic oil tanks for construction machinery such as excavators;

Process: phosphoric acid pickling + phosphating

Problem: After phosphating, a mixed rust remover of phosphoric acid + vegetable acid is used for rust removal, and rust-proof oil is applied after rust removal; after coating and baking, the rust remover and rust-proof oil react to produce some black flaky substances.

Find the reasons

First, there are the following possible reasons for rust residue on the surface after pickling and phosphating:

① The grains of the phosphate film are too coarse or too fine, which reduces the corrosion resistance;

② The free acid content is too high;

③ The surface of the workpiece is over-corroded;

④ The phosphate content in the solution is insufficient;

⑤ There is residual acid on the surface of the workpiece;

⑥ There is a lot of precipitation in the phosphating tank, which has blocked the nozzle;

⑦ The treatment temperature is low;

⑧ Equipment reasons, such as excessive spray pressure, nozzle direction, etc.;

⑨ Rust is not completely removed

Countermeasures

You can appropriately change the existing pickling solution and choose environmentally friendly pickling products, such as MT-708 environmentally friendly rust remover

Secondly, the rust remover and rust preventive oil currently used may be incompatible. In addition, the acidic chemical properties of the rust remover can easily cause the rust preventive oil to undergo qualitative changes under the action of high-temperature baking, and the two chemicals will undergo certain chemical reactions.

Furthermore, in fact, no matter what kind of rust remover and rust preventive oil, a cleaning process is required before rust prevention, so as to ensure that the rust remover will not react with the rust preventive oil. It is more recommended that manufacturers make the following process improvements:

① Industrial cleaning and rinsing should be carried out after rust removal. The rust remover on the metal surface can be cleaned with MT-600E degradable and environmentally friendly cleaning agent, and then rinsed to clean the residual cleaning agent and surface dirt. This will not affect the subsequent use of rust preventive oil.

② After cleaning and rinsing, the surface to be rust-proofed should be dried and cooled (to the rust-proof temperature requirements suitable for rust-proof oil).

③ After applying rust-proof oil, the surface should also be uniform and dry to avoid greasy surface, otherwise it will be contaminated with other pollutants, resulting in poor rust prevention effect.

④ It is best to cooperate with the cleaning agent mentioned above and select rust-proof oil that has been tested for compatibility for rust prevention to avoid chemical reactions between rust remover, cleaning agent and rust-proof oil.

⑤ If you want to replace the rust remover, there are organic acid rust removers and neutral rust removers that can be considered: organic acid rust removers can replace traditional pickling liquid for rust removal, and can also be used as direct rust removers. They are relatively environmentally friendly water-based rust removers; neutral rust removers are environmentally friendly water-based rust removers that do not damage metal substrates and human skin.

⑥ For the above rust removal, cleaning, rinsing, rust prevention and other processes, it is necessary to ensure that the operator wears clean and tidy gloves to avoid the acidic hand sweat of the human body from contaminating the metal surface and affecting the use effect of the cleaning and rust prevention products.

The above is a simple analysis of the possible causes and possible improvement methods. The specific improvement of rust removal, cleaning, rust prevention and other processes needs to be carried out according to the actual production situation and rust prevention requirements.