After the alkaline-etching tank reaches process temperature, foam on the bath surface keeps lifting the liquid level upward; the overflow port hangs with alkali, alkali mist carried out by the exhaust increases, and the drag-out at bath exit and the downstream water wash are both under pressure.

Chemi Tech offers the KM-718 series defoamer for the alkaline-etching and degreasing systems of aluminium-profile surface treatment; the dosage can be adjusted flexibly according to bath temperature and free-alkali concentration. This grade is a high-temperature, strong-alkali-resistant silicone-polyether defoamer that does not break or separate under strong alkali and high temperature. Combined with measured bath-surface foam height and bath-exit drag-out data, the suitable dosage of the KM-718 series can be determined.

Advantages of Chemi Tech Defoamer

Chemi Tech's KM-718 series defoamer is configured for high-temperature, strong-alkali systems. It acts fast — bath-surface foam is broken the instant it returns from the circulation pump; foam suppression lasts long, with no secondary foaming within a bath-change cycle; alkali resistance is good, holding suppression capability as free-alkali concentration rises; heat resistance is outstanding, with breaking not failing even as the bath approaches boiling; compatibility with the alkaline-etching bath is excellent, with no oil separation or wall fouling, keeping tank walls and heating tubes clean; the dosage is economical, graded by free-alkali concentration, and the re-dose frequency drops.

Industry Pain Points and Solutions

The foam problem in the alkaline-etching tank mostly stems from the combined effect of surfactant precipitation after bath heating and circulation-pump shear, ultimately concentrating in two places: overflow alkali hanging and alkali-mist carry-out.

After foam spills over the tank rim, the overflow port hangs with alkali scale, and the floor and tank body need frequent flushing. The dosage of KM-718, graded by free-alkali concentration, keeps the liquid level below the overflow port.

When the profile exits the bath, the liquid film carries foam, and the make-up water of the wash section and the acid-pickling load rise together. KM-718's foam suppression lasts long, and the bath surface recovers flatness during the standing stage before bath exit.

Alkali consumption and re-dose frequency ultimately convert into the treatment cost per tonne of profile. Combined with changes in bath temperature and free-alkali concentration, the dosage can be narrowed to an accountable range, directly reducing alkali replenishment and waste-water-treatment spend.

Typical Conditions and Verification

Customer case: an aluminium-profile enterprise in Guangdong, applied to the alkaline-etching section before anodising.

After grading by bath temperature and free-alkali concentration, Chemi Tech set this workshop's defoamer to KM-718, with the dosage graded step by step by free-alkali concentration. Before this, once the alkaline-etching tank heated above sixty degrees Celsius, bath-surface foam lifted the liquid level over the tank rim, the overflow port was cleared twice a week, and the alkali-mist scale on the exhaust duct kept thickening. After adoption, the bath surface stayed flat within the bath-change cycle; alkali scale at the overflow port dropped markedly; and the make-up water of the wash section and the neutralising acid for waste water fell together.

FAQ

The temperature and free-alkali concentration of the alkaline-etching tank change every day; will the defoamer fail early?

First see whether the defoaming component can maintain a dispersed state under high temperature and strong alkali. KM-718 has completed comparative trials of bath-surface foam and bath-exit drag-out under aluminium-profile alkaline-etching conditions; within the recommended range foam suppression lasts long, and the liquid level stays flat after bath heating and alkali replenishment. The actual dosage is based on free-alkali concentration, with bath temperature and circulation volume as corrections; Chemi Tech determines the suitable plan by comparing bath-surface foam height against bath-exit drag-out.