Fengfan DS 187S Ash stabilizer

Product Overview

What the bath does

Desmutting is the quiet step between the alkali etch and the anodizing tank. The bath that does it here is built on sulfuric acid and hydrogen peroxide, with a Phoenix additive that turns a mild acid dip into a controlled smut remover. Parts come out of the etch carrying a dark, loosely bound layer of alloying elements, and a short dip dissolves it away and neutralizes the alkaline residue left behind. What reaches the anodizing tank is a clean, evenly active surface instead of one that has to be rescued later.

Position matters more than most people expect in an aluminum anodizing process. Placed after the etch rinse and before the anodizing tank, the desmut lets the film build evenly, the dye take without patchiness and the seal close on a surface it can grip. Move it, skip it, or run it on a bath that is past its service life, and the defects surface two or three tanks later, where they are expensive to trace back.

Who runs it

Architectural extrusion, sheet, machined components and general fabrications all pass through the same chemistry. What changes between them is dwell time and bath maintenance, not the tank. A plant that previously ran a nitric acid desmut keeps the same tank position and the same rinse sequence and changes only what is in the tank and what leaves with the rinse water. Small shops working from a compact aluminum anodizing kit run the identical bath in a smaller volume, which simply means it is remade more often.

Key Features & Advantages

• No nitrate to discharge. The bath carries no nitrate, so there is no nitrate in the rinse water and no nitric fume over the tank. Any aluminum anodizing service that has watched a nitrate limit tighten knows where this shows up first: at the drain, not at the tank.
• No chromates in the chemistry. Nothing here is a source of hexavalent chromium, and parts do not leave the tank carrying a chromium-bearing film. Where a chromate conversion coating aluminum route adds chromium to the rinse stream and to waste treatment, this step adds none.
• No fluorides. Fluoride-bearing desmuts need their own effluent control and are hard on glass, titanium and some refractories around the line. This bath has none, which keeps the rinse water simpler and the surrounding equipment out of the argument.
• Built not to upset the anodizing tank. Carry-over is the quiet risk on any industrial metal plating line: whatever leaves the desmut on a rack or in a barrel ends up in the next tank. The chemistry is chosen so that normal drag-out, after a proper rinse, does not disturb the anodizing electrolyte.
• A surface that colours evenly. Smut that is only half removed shows up later as patchy dye take-up or a cloudy electrolytic colour on the anodized aluminum, and by then the parts have been through two more tanks. Full removal at this stage is what makes the rest of the line repeatable on decorative work, where the finish is the product.

Operating Window

Setting Up and Running the Bath

1. Fill with water first. Bring the tank to roughly two-thirds of its working volume, then add the sulfuric acid slowly with the mixer running. Acid goes into water, never the reverse, and the bath should be allowed to cool before the peroxide goes in.
2. Add the peroxide and the additive last. Measure the hydrogen peroxide and the additive into the cooled, mixed acid and stir until the bath is uniform. There is no digestion or heating step to wait for; the bath is ready once it is mixed and at strength.
3. Size the tank to the biggest load. The largest rack or barrel you run has to be fully immersed with room to move, and a full load should not use up the peroxide before the shift ends. On a small aluminum anodizing kit line that usually argues for a taller, narrower tank rather than a wide shallow one.
4. Watch the peroxide before the acid. Hydrogen peroxide is the component that falls away first: it decomposes slowly on its own and faster when the bath is warm or carrying metal fines. Check it regularly and top up to keep the bath inside its working band, while the acid figure moves far more slowly. On a busy industrial metal plating line this is the one check to put on the shift sheet.
5. Read the bath from the parts. Dissolved aluminium builds shift after shift. The first sign is time: work that used to clear quickly starts needing longer in the tank. When that happens the bath is near the end of its life, and it is better to discard and remake it than to push on and risk a smut film that only appears once the anodizing aluminum process is finished.
6. Rinse properly before the next tank. A clean rinse, in two stages if the line has them, is what keeps drag-out out of the anodizing electrolyte. If parts still smell of acid or peroxide coming out of the rinse, the rinse is too short.

Alloys and Surface Conditions

Alloy by alloy

Smut is an alloy question. Nearly pure aluminium and low-alloy sheet come out of the etch with a light grey film that clears almost at once. Extruded 6xxx profiles, which carry silicon and magnesium, throw a darker, thicker smut and hold on longer. High-silicon casting alloys, and copper-bearing 2xxx and 7xxx grades, are the heaviest of all: these are the loads where the upper end of the dwell earns its place, and where the first dull haze appears on the anodized aluminum if the bath is past its service life.

Mixed order books

A part that has been mechanically polished or brushed holds smut in the direction of the scratches, and a recess can keep a shadow that only becomes obvious after anodizing. Across a mixed schedule in an anodizing aluminum process, prove the heaviest alloy first rather than the easiest: if the worst load comes out clean at a sensible dwell, everything else will follow. Inspect parts while they are still wet — a residual film shows there as a dull haze long before it shows on a dry part.

Tank, Handling and Storage

1. Use a tank and lining rated for acid plus oxidizer. Sulfuric acid at working strength with hydrogen peroxide in it is not kind to mild steel or bare concrete. Confirm the tank, the lining and the seams before the first fill — in the metal plating process this is the step where a tank selected on purchase price alone turns out to be the expensive choice.
2. Ventilate the tank area. The bath gives off oxygen as the peroxide works, and acid mist is present whenever the tank is open. Local exhaust at the tank lip keeps the working area comfortable and keeps the mist off nearby equipment. It matters most where a small aluminum anodizing kit sits in a shared workshop rather than in its own bay.
3. Store the concentrate closed, cool and shaded. Keep it out of sunlight and away from heat, and away from anything that would catalyse peroxide decomposition. Rotate stock rather than leaving it at the back of the store.
4. Handle it as an industrial chemical. Eye protection, acid-resistant gloves and an apron are standard on an industrial metal plating line, and they apply here in full. Ask your sales contact for the current SDS before the first make-up and keep it with the bath records.
5. Deal with the spent bath deliberately. A spent desmut carries dissolved aluminium and residual peroxide. Neutralize it and send it through the plant's existing waste treatment rather than to drain, and check local discharge limits before the first discard.

Other Chemicals on the Same Line

• Before the etch: Phoenix Clean 151. A degreasing and dewaxing powder for the step ahead of anodizing. Polished parts carry wax that a plain alkaline cleaner leaves behind, and in the aluminum anodizing process that wax becomes exactly the kind of patchy film the desmut cannot fix.
• The etch itself: Phoenix Etch 660. An alkali-etch additive that holds dissolved aluminium in the bath and keeps pitting back, so the etch delivers the even matte the desmut then has to clear.
• Colouring: Phoenix EB 204A-204B. A phenol-free divalent tin electrolytic colouring set for the step after anodizing. Colour follows the film, which is why in any metal plating process the pre-treatment decides what the finish looks like.
• Sealing: Phoenix Seal 149-T and Phoenix Seal 149-L. Nickel acetate sealers for medium-temperature sealing after dyeing or electrolytic colouring, run in stainless steel tanks.
• A different route entirely. Where a shop runs a chromate conversion coating aluminum process instead of anodizing, this desmut is not part of it — that line has its own pre-treatment sequence and its own chemicals.
• When the order book keeps changing. Job shops running an aluminum anodizing service for several customers see the alloy mix shift week to week. Keep the bath on the strong side of its range and prove each new alloy on a scrap part before it goes on the line.

Ordering & Delivery

Technical Support & Model Matching

Choosing the right match is where most sourcing decisions stall. As a trading supplier, we keep one point of contact from first enquiry to after-sales: tell us what you are making and the conditions you work under, and we shortlist the closest matches from our supplier network, compare specifications and arrange samples before you commit to a bulk order. If something does not behave as expected, we work with the supplying partner on the cause and a practical fix, and stay with the case until it is settled. Email, WeChat or WhatsApp enquiries get a reply within 24 hours.

FAQ