Electroplating guide · Updated August 2026 · Reading time about 9 minutes
Anyone choosing an anode bag for a plating line runs into three numbers straight away: 5, 15 and 25 microns. The obvious assumption is that smaller is better. In practice the choice is more differentiated. The nominal micron rating is only part of it; the construction of the material, the composition of the electrolyte, the solids load and the permeability you need all come into it as well.
This guide sets out how the three anode bags in the WINKLER range differ, which grade is intended for which situation, and what to measure before you order. Everything that can be ordered directly is in the category anode bags and cathode bags for electroplating.
Key points at a glance
15 µm The economical standard grade for general electroplating work.
What the micron rating means
The figure in microns describes a property of the filter material in use. It helps you place different materials and compare them with each other. It is not…
The short version
15 µm The economical standard grade for general electroplating work.
5 µm The finer grade, when a finer nominal material specification is what the process needs.
25 µm Calendered monofilament fabric for organic-rich electrolytes and released bright nickel baths.
In this guide
What the micron rating means
Anode bag material: three constructions
The 15 micron grade
The 5 micron grade
The 25 micron grade
The three grades compared
Four common wrong turns
Anode bag sizing: what to measure
Choosing in six steps
What to send us
Frequently asked questions
What does the micron rating on an anode bag mean?
The figure in microns describes a property of the filter material in use. It helps you place different materials and compare them with each other. It is not a guaranteed absolute cut-off for the finished anode bag.
How the bag behaves in a plating process also depends on the shape and distribution of the particles, the solids concentration, bath agitation, the filter cake that builds up and the condition of the material. A nominal value of 5 microns therefore does not mean that every larger particle is fully retained under all operating conditions.
Permeability plays a part too. A very fine material can blind faster under a high solids load than a coarser one. The right choice comes out of a balance between the retention you want and enough mass transport in the process.
Technical note. The micron rating places the filter material. For a practical choice, the electrolyte, solids load, anode shape and operating conditions have to be looked at as well.
Anode bag material: three constructions, not one scale
The question most buyers ask second, and should ask first, is about the electroplating anode bag material rather than the number printed next to it. All three grades are polypropylene. What separates them is how that polypropylene is built.
A woven staple fibre fabric is made from yarn spun out of short fibres. It has a slightly hairy surface, good mechanical resilience and separates at the plane where the yarns cross.
A needle felt has no such plane. Fibres are laid down without orientation and entangled mechanically, giving a three-dimensional pore system with a high void fraction that separates through its depth.
A calendered monofilament fabric is woven from single smooth continuous filaments and then compacted under pressure between rollers. It has the most closed surface of the three and defined openings.
Note that “anode bag material” is also a common search term in the cathodic protection trade, where it refers to the cloth and backfill around a sacrificial anode. That is a different product for a different industry. Everything here refers to plating and anodizing tanks.
The 15 micron anode bag: the standard grade
The 15 micron anode bag is the first choice for many classic plating applications. It is a washed and thermofixed PP fabric and comes in six sizes for anode baskets, plate anodes and billet anodes.
It suits the case where an economical standard bag is what is wanted and there is no particular requirement for a very fine structure or a smoothed monofilament surface. That makes it easy to place in an established process.
This grade often fits when:
an economical standard solution is what you need,
a nominal rating of 15 microns is specified,
anode baskets, plate anodes or billet anodes are in use,
a directly orderable standard size is available, or
a made-to-measure version is needed for different dimensions.
If the bag you use today works reliably and has a comparable material structure, the 15 micron grade is usually a sensible starting point.
The 5 micron anode bag: when a finer grade is needed
The 5 micron anode bag is a thermally smoothed PP needle felt. Its nominal rating is finer than the 15 micron standard grade.
It comes into question when particularly fine particulate residue matters in the process, or when experience so far calls for a finer material specification. It is always worth checking whether the finer rating suits the solids load and the permeability the process needs.
The 5 micron bag is not automatically the better solution in every process. Under a high particle load a finer material can be blinded sooner. What decides is the job the bag has to do in the specific bath, and how regularly it can be checked and changed.
This grade is worth looking at when:
a finer nominal specification than 15 microns is required,
fine particulate residue is critical in the process,
there is experience with a comparable needle felt quality, and
solids load and required permeability are assessed together.
The 25 micron anode bag for organic-rich electrolytes
With the 25 micron anode bag the micron rating is not what decides. The product is a calendered PP monofilament fabric with a smoothed surface, intended for organic-rich electrolytes and for bright nickel baths released for it.
Organic constituents can behave differently on a filter medium than purely particulate residue, depending on the bath. That is why this grade was not designed as a coarser alternative to the standard bag but as a specialist solution with a different construction.
This grade can be the right one when:
the electrolyte carries a high organic load,
a smoothed monofilament surface is what is needed,
use is intended in a bright nickel bath released for it, or
a staple fibre weave or a needle felt does not suit the application.
Whether it is suitable for a particular nickel bath should be assessed from the bath chemistry, concentration, temperature and operating experience so far.
The three grades compared
| Grade | Material and construction | Air permeability | Particularly suited to |
|---|---|---|---|
| 15 µm | Woven PP staple fibre yarn, washed and thermofixed, 320 g/m² | 50 l·dm⁻²·min⁻¹ | General electroplating and an economical standard solution |
| 5 µm | PP needle felt, thermally smoothed, 400 g/m² | 125 l·dm⁻²·min⁻¹ | Processes needing a finer nominal specification |
| 25 µm | Calendered PP monofilament, 370 g/m², 5 sizes | 25 l·dm⁻²·min⁻¹ | Organic-rich electrolytes and released bright nickel baths |
Read the middle column and the right-hand one together and the point of this guide appears: the ratings fall from 25 to 5, and permeability falls the other way, from 125 down to 25. The finest grade is the most permeable of the three and the coarsest is the tightest, by a factor of five.
That is not a contradiction. A needle felt has a large void volume between its fibres and separates through its depth, so it can be specified fine and still let a lot through. A calendered monofilament weave has been compacted at the surface, which closes it. The staple fibre weave sits between them.
All three permeability figures are stated by the fabric supplier and were measured on flat, dry material with air. They compare the three grades with each other. They are not a statement about how much electrolyte moves through a finished bag in a running tank, and two permeability values are only comparable at the same test pressure.
The micron ratings are nominal supplier values as well. They do not represent a guaranteed absolute cut-off for the finished anode bag in a plating process.
Why 5 microns is not automatically better than 15
A smaller number looks like the safer choice. It can be, when fine particles really are the problem. At the same time the electrolyte still has to get through the material, and depending on solids load a finer structure can be blinded sooner.
So a 15 micron bag that has proved itself should not be replaced by a 5 micron one purely because the number is lower. What matters is what the process requires. With organic-rich electrolytes, in turn, the construction of the 25 micron bag can matter more than any comparison of the ratings.
Four common wrong turns
1. Choosing the lowest micron figure. A finer nominal specification is not automatically better for every process. Solids load, permeability and change interval have to be considered with it.
2. Overlooking the construction. Woven staple fibre, needle felt and calendered monofilament differ in structure and surface. That is why the 25 micron grade is not placed by its rating alone.
3. Treating air permeability as liquid throughput. Air permeability is a material figure measured dry on flat fabric. It does not describe how the finished bag behaves in your electrolyte under a real solids load.
4. Checking dimensions and suspension too late. Material and rating only help when the bag fits the anode shape, the opening and the existing suspension.
Anode bag sizing: what to measure before you order
More returns come from dimensions than from ratings, so it is worth taking five minutes with a tape measure. Anode bag sizing comes down to four figures and one photograph.
Length. Measure the anode or the anode basket over its full immersed length, then add enough for the bag to be closed or tied above the bath line. A bag that ends at the liquid surface is a bag that will be pulled off.
Width. For a plate anode, measure the flat width and allow for the bag to lie against it rather than stretch over it. For an anode basket, measure the widest cross section including any frame, not the nominal basket size.
The opening. State the opening you want and how it is to be closed, whether that is a hem, a tie or an open top. This is where most made-to-measure enquiries stall, because it is the one figure nobody thinks to record.
Corner radii on baskets. Titanium baskets in particular have corners that load the fabric at a single point. If the corners are sharp, say so; it changes what we recommend.
A photograph of the installation. One picture of the anode in the tank answers more questions than a page of description, above all about the suspension.
The six standard sizes run from 160×80 mm up to 1250×375 mm, and the 25 micron grade covers five of them. For anything else we make the bag to measure.
Further selection criteria beyond the rating
Anode shape and dimensions. The bag has to suit the anode in use, and it makes a difference whether an anode basket, a plate anode or a billet anode is being enclosed. A bag that is too wide sits badly; one that is too tight is awkward to fit and takes unnecessary load.
Electrolyte and temperature. All active anode bags in this range are polypropylene and are intended for a maximum working temperature of 90 °C. Beyond that, whether the specific material grade suits the composition and concentration of the electrolyte has to be checked.
Solids load and change interval. The more particulate residue is produced, the faster the filter material loads up in service. The right rating therefore also depends on how quickly anode sludge forms and how often the bag can be checked or changed.
Surface of the filter material. Staple fibre weave, needle felt and monofilament weave have different structures. The 25 micron grade is defined by its calendered monofilament weave rather than by its nominal rating.
Standard size or made to measure. Common dimensions are available as directly orderable standard sizes. For different anodes or baskets an anode bag can be made to measure.
Operating experience so far. A grade that has already proved itself is an important reference point. The material, rating, dimensions and change interval of the bag in use make choosing a replacement much easier.
Choosing an anode bag in six steps
Define the application. Is this general electroplating work or an organic-rich electrolyte?
Record what you use today. Which rating, which material and which dimensions have been in use so far?
Place the particle load. Is fine residue critical, or is a reliable standard solution the priority?
Measure the anode. Length, width or circumference, opening and suspension.
Take the electrolyte and temperature into account. Match medium, concentration and working temperature against the material grade.
Choose a standard size or a special. Order the size that fits or ask for a made-to-measure version.
What to send us
The more precisely the existing version and the process conditions are described, the better we can tell whether a standard bag fits or a special size is needed.
Electrolyte. The medium, plus known concentration and relevant additives.
Working temperature. The usual range in the running process.
Anode shape. Anode basket, plate anode, billet anode or a different geometry.
Dimensions. Length, width or circumference, opening and type of suspension.
Version in use. Material, nominal rating and any known product designation.
What you are seeing. Which particulate residue or change in behaviour prompted the review?
Frequently asked questions about choosing an anode bag
Answers to the most common questions about this topic.
Is a 5 micron anode bag always better?
No. The finer nominal specification can make sense in certain processes but is not automatically better for every application. Solids load, permeability, electrolyte and change interval have to be taken into account as well.
What does nominal micron rating mean?
It is a way of placing the filter material in use. It is not a guarantee that in the finished bag, under all process conditions, every particle above that value is fully retained.
Why does the specialist grade for organic-rich electrolytes have the coarsest rating?
Because the rating is not the point of that grade. What matters is the calendered PP monofilament weave with its smoothed surface, which is intended for organic-rich electrolytes and released bright nickel baths.
Can the air permeability figures be compared directly?
Within this range, yes, because all three come from the fabric supplier. They are not a guaranteed liquid throughput for the finished bag. In the electrolyte, solids load, filter cake, agitation and installation all affect actual behaviour. Two permeability values from different sources are only comparable at the same test pressure.
What temperature do the anode bags withstand?
The active grades are polypropylene and are intended for a maximum working temperature of 90 °C. Suitability for the specific medium and its concentration should be checked separately.
Can anode bags be made to measure?
Yes. Alongside the directly orderable standard sizes, WINKLER makes individual dimensions. For that we work from the anode shape, external dimensions, opening, suspension, electrolyte and working temperature. Use our product advice for anything outside the standard range.
The anode bags in this guide
Standard. 15 micron anode bag. The economical standard grade in washed and thermofixed PP fabric.
Fine. 5 micron anode bag. The finer grade in thermally smoothed PP needle felt.
Specialist. 25 micron anode bag. Calendered PP monofilament for organic-rich electrolytes.
Not sure whether 5, 15 or 25 microns suits your process, or does no standard size match your anode? Through our product advice we go through the dimensions, the medium and the requirements together. Everything that can be ordered directly is in the category anode bags and cathode bags for electroplating.
Related reading: anode sludge in the plating bath.
Still unsure which filter or next step fits?
Send us the medium, dimensions and application. We will help you decide whether a standard product is suitable or whether the case needs a custom solution.
Open filtration product advice
