Fengfan Alkaline Etching Additive AE-101

Product Overview

The etch decides what the rest of the line can do. This additive is what lets that step run on caustic soda instead of acid: added to a 45% NaOH etch bath, it replaces the traditional acid etch in the aluminum anodizing process, and with it the acid mist, the acid drag-out and the acid waste stream the old bath produced. The working environment around the tank changes as a result, not just the chemistry in it.

The gain is not only environmental. The etch-back — the pass that strips mechanical polish and opens a uniform surface — runs faster than traditional acid polishing, so the same tank clears more work in a shift and a heavy etch stops being the slowest point on the line.

Nothing is deposited in this bath. It is an etch, not a metal plating process: the caustic dissolves a thin layer of the aluminum itself, taking extrusion lines, handling marks and residual polish with it, and the part leaves the tank slightly lighter than it went in.

It suits aluminum and aluminum alloy parts — extrusions, sheet, profiles, machined components and die-castings — and it is used on work that leaves the line as anodized aluminum, where any unevenness in the etch would show straight through the film.

Bath Make-Up & Replenishment

Caustic Soda Control

The 45% caustic soda is the component that does the cutting. It is the largest charge in the bath and the widest range in the table above, and the width is deliberate: a light etch-back on thin extrusion and a heavy matte etch on a thick die-casting pull very different amounts of aluminum, so the charge follows the work rather than a fixed recipe.

The bath drifts while it works. Free caustic falls as it is consumed, and dissolved aluminum rises as metal goes into solution; both slow the etch, and both move at a different rate on different work. A metal plating process can often be run from ampere-hours alone; an etch cannot, which is why the charge here is set from analysis of the bath rather than from the number of racks that have been through it.

Over-charging does not buy a better surface. Caustic pushed harder etches faster than the part can take it, rounds machined edges and shortens the life of the bath; under-charging leaves the surface smeared and the film that follows uneven. Neither fault is visible until the parts come out of the anodizing tank.

The pattern differs by plant. A job shop running an aluminum anodizing service on outside work sees more variation than a captive line running one product family, and for that shop the caustic analysis is the only stable reference between jobs.

In aluminium anodizing plants that run several alloys through one tank, the same rule holds: match the caustic charge to the alloy and to the removal you want, then correct on the analysis rather than on the calendar.

Water & Bath Volume

1. Charge the water first, into a clean tank that tolerates hot caustic, and use water low in hardness and chloride — a deionized line is the safer choice where the plant has one, because hardness salts and chloride both disturb an even etch.
2. Bring the bath to temperature before the first rack goes in. An etch started cold treats the first rack differently from the tenth, and the difference reappears later as a tone shift across a batch.
3. Top up on production, not on the clock. In the aluminum anodizing process the etch tank is one of the larger water users on the line, losing volume to evaporation and to drag-out on the work, so replenishment follows the piece count in the same way the other two components do.
4. Add make-up water gently and away from the work. Cold water dropped into a hot bath cools a patch of it, and that patch etches differently from the rest of the tank until it has mixed.
5. Treat the rinse as part of the water balance. Drag-out carries caustic into the rinse tank, and a rinse that is not overflowing carries it back onto the next rack of parts.
6. Size does not change the ratio. The same water-to-caustic relationship holds from a small aluminum anodizing kit up to a full production line; the tank is simply bigger.

Additive Dosing

• Charge against the bath, not against the drum. The make-up charge is 2~3 L for the working bath shown in the table, replenished at 140~200 per 480 pcs. The additive is a small fraction of the caustic charge and is meant to stay that way.
• Dose against the caustic. When the caustic goes to the top of its range for a heavy etch, the additive moves with it; when the work is light, both come down. Ratio first, absolute volume second.
• Replenish on pieces, not on hours. The replenishment range covers light sections and heavy castings, and a line doing one will not land in the same place in it as a line doing the other.
• Watch the thinnest section on a mixed rack. When you anodize aluminum parts of different thickness together, the thin sections etch first and the heavy ones catch up, so sampling the worst part tells you more than sampling the average.
• Judge the etch on the darkest work you run. A black anodized aluminum panel shows a patchy etch that a clear film never reveals, which makes dark work a quick early check on whether the additive is going in evenly across the shift.
• Check the additive before the caustic. If the etch-back slows while caustic and temperature are both inside their ranges, the additive is usually the component that has been under-replenished — and adding caustic to fix it only makes the bath harder to bring back.

Process Sequence & Line Compatibility

1. Degrease and dewax first. The etch removes aluminum, not oil; polish wax and cutting fluid have to be off the part before it reaches the caustic, or the bath spends its charge on contamination.
2. Rinse on both sides of the etch. Carry-over from the degrease neutralises caustic, and carry-over from the etch neutralises the electrolyte in the next tank.
3. Rack for the etch, not for the anodize. When you anodize aluminum parts that came off a polishing wheel, the polished faces are the ones that show every contact mark, so they belong in the flow of the bath rather than pressed against a bar.
4. Desmut before anodizing. An alkaline etch leaves a smut of alloying elements — copper and silicon are the usual ones — and it comes off in a desmut dip chosen for the alloy rather than for the tank.
5. Anodize, colour, then seal. The etch sets the surface the film grows from, so unevenness here becomes unevenness in the anodized aluminum finish however well the later tanks are run.
6. Plan the colour step with the etch in mind. Work that ends as black anodized aluminum is judged on evenness of colour, and that evenness is decided in the etch tank rather than in the dye.
7. The rest of this line comes from the same supplier: Phoenix EB 204A-204B divalent tin salt electrolytic coloring additive for colour after anodizing, and Phoenix Seal 149-L and Phoenix Seal 149-T for medium-temperature sealing once the colour is on. Beyond the anodizing line, the range covers SZ-30B sulfate zinc brightener, ZN 50 and ZN-500 alkaline zinc processes, FI-970 bright acid copper, Nickel Purify P3 for nickel bath purification, FF-116 chrome mist inhibitor, and FF-4219 for wood, stone and concrete.

Storage & Handling

• Keep it sealed, and use it within 6 months. The additive is supplied to be stored sealed, and the nearer it goes into the bath to its delivery date, the less of it the line spends.
• Keep it out of the sun and away from heat. A drum parked beside the etch tank or on a sunny loading bay sits in exactly the conditions the product is meant to avoid.
• Do not stir or shake before use. The additive goes into the bath as supplied; mixing only puts air into it.
• Never blend leftovers with expired stock. Part-used drums stay separate and labelled — a blended drum cannot be dosed against the figures in the bath table.
• Handle it as an alkaline chemical. Eye protection, gloves and an apron at the drum, and the same discipline at the tank, where the bath runs hot.
• Ask for the safety data sheet with the batch. Your sales contact can send the current SDS for the batch you receive, together with the transport documents the carrier asks for.
• Store against the next make-up, not the next delivery. In a plant running aluminium anodizing continuously, the drum in use sits near the tank while the reserve stays sealed and shaded; keeping those two roles apart is what protects the six-month window.
• Size the reserve to the window. A small aluminum anodizing kit draws stock down slowly, so keep the reserve to what the line will actually use inside six months rather than stacking drums that will not be opened in time.
• Keep a drum log. Shops running an aluminum anodizing service change alloys and loads daily, and a note of which drum went into which bath — and when — is the difference between tracing a bad week and guessing at one.

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