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ThicknessThe choice of the most suitable anodizing thickness, and consequently the thickness of G.H.A.® treatment, should be based on the specific needs and desired performances of customers. The thickness range is from 5 to 200 µm, depending on the specific aluminium alloy used.Here are the maximum achievable oxide thicknesses for some of the main alloys that are suitable for anodization:5000 AND 7000 SERIES : maximum thickness 150-200 µm;6060 ALLOY: maximum thickness 100-150 µm;6082 ALLOY: maximum thickness 80-100 µm;CASTING ALLOYS: To be evaluated case-by-case depending on its composition and homogeneity.The most suitable choice for each customer must always be based on a cost/performance ratio. GHA Europe® is available to appropriately evaluate it together to help reach the best solution.

AlloysAs it is well known, aluminum is a metal with excellent characteristics, but it is limited by poor mechanical properties. For this reason, aluminum-based alloys were developed to enhance the characteristics of the base material with the addition of various elements that confer their properties in a specific combination to suit different needs.The choice of an aluminium alloy suitable for anodization must be made based on several factors:Cost;Ease of processing;Mechanical properties;Anodic oxide quality;Availability;Traceability;Repeatability;Compatibility with standards and regulations.It is important that the choice of the alloy is based on the field of application and the requirements to be achieved.SERIES 1000 – Al 99%Suitable for food applications. Low mechanical properties, but excellent anodizing behavior.SERIES 2000 – Al-CuNot suitable for food applications. Exhibits poor anodic oxidation performances.SERIES 3000 – Al-MnSuitable for food applications. Limited use in mechanical applications and rarely processed through anodizing.SERIES 4000 – Al-SiPotentially suitable for food applications depending on composition.Appropriate for anodizing if the silicon content is below 9%. Evaluation is required on a case-by-case basis.SERIES 5000 – Al-MgSuitable for food applications. Medium mechanical properties.Good anodizing performance, but typically with a less refined aesthetic finish due to higher porosity.SERIES 6000 – Al-SiMgSuitable for food applications. Medium mechanical properties and good corrosion resistance.Excellent anodizing results with high-quality aesthetic and technical finishes.SERIES 7000 – Al-CuZnNot suitable for food applications. Good mechanical properties but low corrosion resistance.Good anodizing performance with excellent final mechanical properties, though corrosion resistance is inferior compared to other alloys, with potential risk of defects (see the "defects" section of the FAQs).G.H.A. Europe® is available to provide any advice towards the choice of the most suitable alloy and treatment according to the customer's needs.

TolerancesDimensions and tolerances must be calculated before manufacturing the parts, based on the required treatment thickness.Aluminium oxide (and consequently G.H.A.® treatment) grows directly onto the aluminum substrate, penetrating approximately for half the total thickness. This means that, on a flat surface, a 50 μm total treatment thickness will generate a net traslation of the surface of about 25 μm towards the exterior.For this reason if we talk about tolerated holes the final diameter decrease would be the same as the thickness of applied treatment. This means that a tolerated hole on a part that requires 50 µm of treatment has to be initially 50 µm wider than the desired final diameter.In many cases it is also possible to mask tolerated areas and holes with caps, chemically resistant adhesive tape or special paints. In this case it is best to calculate those dimensions using the final values, because they will not be affected by the treatment.

Localized treatmentIf some treated parts require specific modifications and localized reworking, it is possible to re-perform the treatment only in those areas, without altering the existing oxide layer.It is essential that the machining reaches the bare aluminum substrate, that the reworked surface is uniform and clean (see example images below) and that the edges are adequately rounded to ensure an optimal final result.Parts made of 7000 and 2000 alloys present greater risk of deterioration when retreated, as they are less resistant to the acidic products used in the anodization process, especially if they were not properly sealed during the first treatment. For this reason, we cannot guarantee that parts not originally treated by GHA Europe® will yield optimal results after the retreatment.

DeoxidationsAnodic oxidation is a treatment that can be attacked by highly acidic and basic solutions.Thanks to controlled baths of nitric acid and sodium hydroxide, we can chemically remove the treatment (deoxidation) so that it can be re-performed according to the customer's specific requests.When choosing to deoxidize parts, it is necessary to take into account their dimensions and tolerances as the treatment penetrates the aluminum substrate for half its thickness, so removing it means directly eroding the surface of the base metal.In this case we can proceed in two alternative ways:It is possible to mask holes or other areas with special caps, tapes or paints to prevent their surface from being affected by deoxidation (and subsequent re-treatment);It is possible to treat the parts after deoxidizing so that the new oxide thickness value restores their dimensions to about their original state. Following this method generally means reaching an oxide thickness that is more than double of the original value.E.g. To restore a deoxidized part that had a thickness of 20 µm of oxide or GHA®, it will be necessary to re-oxidize the part with a treatment thickness of at least 40 µm.In any case, all assessments must be made on a case-by-case basis, measuring (if necessary) the parts before and after the treatment with specific equipment to guarantee the success of the process.Another aspect of deoxidation is the substantial deterioration of the surface finishing because of increased roughness and porosity, especially when removing very thick oxide layers or retreating certain alloys. In most of these cases we can restore ouselves the surface finishing by brushing and polishing it or we can recommend to the customer the most suitable pre-treatment finishes for a proper restoration.Sometimes it can be more convenient, considering the final result, to rework some specific areas.

ColorsThe addition of silver, intrinsic to GHA® technology, affects the interference of light that passes through the oxide layer, resulting in a characteristic set of colors that depends on the aluminum alloys used (series and metallographic structure) and the oxide thickness. It is therefore good practice to submit reference samples prior to production (sampling is usually provided free of charge).We would like to point out that GHA® is a performance treatment (it has antibacterial, anti-wear, anti-corrosion and other properties) and not a color treatment. What is of the utmost importantance for us is to guarantee the achievement of our customer's specific technical specifications.Obviously, where requested, we can provide the customer with a color as close as possible to the desired one, compatible with the colorimetric range possible with GHA®.In this regard, it is important to keep in mind that color is primarily influenced by the alloy and, secondarily (but no less importantly), by its metallography. Surface finish (satin, polishing, tumbling, sandblasting, etc.) is also a variable that must be verified through preliminary sampling. It is therefore possible for two parts made from alloy 6082 to have different colors even with the same treatment thickness and despite being made in the same wet process. Unfortunately, even parts made from the same bar can be different colors, as illustrated in the FAQ " Can parts made from the SAME BAR be a DIFFERENT COLOR ? "

DefectsThe corresponding AITAL (Italian Association of Aluminum Surface Treatments) monographic factsheet can be consulted at www.aital.net/download/schede-difetti . Below, however, we illustrate the main defects that can be found.Surface BollosityA typical defect of 7000 series alloys (rarely observed in other alloys), consisting of swelling of the superficial oxide layer.This phenomenon is caused by the presence of oxides or other heterogeneous particles trapped in the surface (cortical) areas of the extruded material, often associated with gas inclusions. During the thermal cycles involved in oxide formation and sealing, these inclusions tend to migrate toward the surface, generating localized swelling of the anodized layer.These “bubbles” create weak points in the oxide layer. When subjected to abrasion (e.g. with abrasive paper), they may rupture, exposing the underlying base metal.Various corrective actions can be evaluated on a case-by-case basis to minimize or mitigate the issue. However, since these defects often result in actual micro-craters in the base material, simply removing the oxide layer is not sufficient. Proper mechanical reworking is required before retreatment.Flames, Streaks or BandsThis defect is often not visible before anodizing and may only become evident after surface preparation (etching or pickling). After anodic oxidation, it appears as areas with different shades (lighter or darker) compared to the surrounding surface.The root cause is typically linked to an uneven distribution of intermetallic phases or heterogeneous particles within the base material.Components affected by this defect are difficult to recover through anodizing alone. Certain finishing techniques may reduce its visual impact, but complete elimination is rarely achievable.Welding EffectWelding on aluminum components intended for anodizing can lead to aesthetic inconsistencies, even when performed correctly.It is essential to use a filler material compatible with the base alloy. However, due to the thermal stresses introduced during welding, the affected area may exhibit differences in microstructure, resulting in visible color variations after anodizing.Pre-Treatment Corrosion DotsAluminum, particularly 7000 series alloys, is prone to spontaneous oxidation. If components are left wet after machining (with water or machining oils), corrosion may occur.In some cases, corrosion is visible and can be removed through appropriate pre-treatment finishing. In other cases, corrosion defects may be subsurface and only become evident after anodizing, leading to an irregular or defective oxide layer.The only effective solution is:Deoxidizing the componentPerforming mechanical reworking to restore surface uniformity (if tolerances allow)Reapplying the anodizing treatment

All parts treated with anodic oxidation, and consequently with GHA® technology, are sensitive to excessively acidic or basic pH, it is therefore recommended to clean the affected areas with preferably neutral or medium-aggressive washes, whose pH falls within a range of 4 to 8.5. The following are not recommended: Washes with excessively basic components (Ph>8.5), especially if carried out at temperatures above room temperature; Washes with excessively acidic components (pH<4), especially if carried out at temperatures above room temperature. GHA® is an antibacterial treatment (bactericidal action), therefore it does not require particularly aggressive cleaning on its surface, suitable for sanitizing parts intended for contact with food or pharmaceutical products. The good non-stick properties of the GHA® treatment facilitate the removal of dirt and encrustations, allowing for effective cleaning even with mild washes or with the use of abrasive cloths (such as sponges and kitchen scouring pads). Recommended: Washing with demineralized water can also be carried out with high-pressure, high-temperature pressure washers; Steam cleaning; Washing with medium-aggressive detergent products with a pH between 4 and 8.5; Washing with solvents (acetone, alcohols). GHA Europe® is available to provide advice on the type of washes and detergents to use based on the customer's needs, conducting targeted laboratory tests if necessary, and also offering to develop dedicated solutions in collaboration with manufacturing companies.

PURCHASE ORDER (PO)The Purchase Order document accompanying the material shipped to GHA Europe must contain the following information:The wording "Processing account" or equivalent if the material is to be treated normally; the wording "Repair account" or equivalent if the material is to be treated under warranty or the wording "Viewing account" or equivalent if the material is free samples (previously agreed upon) or similar;The drawing number (or code) of each type of part sent, with the quantity, the type of treatment required and its thickness next to it;Any additional work to be carried out on the parts, such as protection from treatment, brushing, polishing, ...;Any requested delivery dates, which must be clearly visible on the delivery note;The possible presence of drawings to be returned with the details treated;The address to which the treated material will be shipped and the shipping method (recipient collection; collection by a carrier called by the recipient, collection by a carrier paid by GHA, etc.).

PackagingIf the parts are transported by a carrier, to preserve their integrity, it is recommended to use rigid packaging made of metal, wood, or plastic, inside which the parts are prevented from moving and colliding with each other. It is recommended to apply at least one layer of bubble wrap to separate each part. As the part's mass increases, the amount of padding surrounding it should also be increased.If it is not possible to use rigid packaging, we recommend at least insuring the shipment against possible damage caused by transport.

Delivery times and urgenciesFor medium-sized supplies (less than approximately two standard pallets), we can guarantee processing within 5 working days of receiving the material, excluding complications not caused by GHA Europe®. The exception is semi-hard anodic oxidation, which is usually only performed on Monday mornings; therefore, material requiring this treatment cannot be ready before that day.If the customer needs the item to be returned sooner, it is possible to request urgent processing by adding a supplement to the total price:Delivery within 48 hours: +15%;Delivery within 24 hours: +25%;Same-day delivery (morning to evening or afternoon to next morning): +40%.The minimum emergency surcharge is €50.00 + VAT. This may vary if the items in question present particular critical issues.Urgent requests must be made by clearly indicating the requested delivery date (and time) on the delivery note and, if possible, by calling or sending an email to notify the customer of the incoming material.It is not always possible to carry out the treatment with the required urgency, in which case GHA Europe® will contact the customer immediately to arrange another delivery date.It's also important to consider shipping times, which for large carriers like GLS, BRT, DHL, UPS, etc., generally exceed 24 hours from pickup. Pickups with these carriers must be booked by 12:00 noon on the day of delivery, and the items must be ready for pickup by 2:30 pm the same day.GHA Europe® can arrange both national and international collections and deliveries through its partner carriers, GLS, BRT, DHL, and UPS.

Treatment CostThe easiest way to recieve a quote for the treatment cost of a specific component is to send its technical drawing in STEP format (preferred) or PDF to: ghaeurope@gmail.comRequired Information:To provide an accurate quotation, the following data is required:Type of treatment (G.H.A., Hard Anodizing, etc.)Required thickness (e.g. 20 μm, 45–55 μm, etc.)Aluminium alloy used (e.g. 6082, 5083, etc.)Any additional operation (cleaning, surface preparation, masking, etc.)Estimated quantityTechnical Support:If some of the above information is not available, G.H.A. Europe® can support you in defining the optimal parameters.For example, if the required thickness is unknown, it is sufficient to provide:The type of previous treatmentThe function of the componentThe type of wear or corrosion to be preventedBased on these inputs, G.H.A. Europe® will recommend the most suitable treatment specifications.The company is also available to perform sampling tests and lab tests if validation is required.Pricing Method:The treatment cost is calculated according to the following guidelines:Surface Calculation The total surface area of the component is determined, typically using the technical drawing. The STEP format is ideal, as it allows an immediate and precise calculation. Price per Unit Area The surface value is multiplied by a price per square decimeter (dm²). This value mainly depends on: In general, the unit price slightly decreases as the size of the component increases.Type of treatmentRequired thicknessAdditional Costs:A surcharge may be applied in the following cases:Parts with small surface area but large volumeComponents requiring special mounting or handlingAlloys not suitable for anodizingParts requiring pre-treatment (cleaning, finishing, masking, etc.)Masking or local anodising Urgency Factor:In case of urgent delivery, the total cost may be increased by a factor depending on the required lead time.