A minimum purity specification of 98% for electroplating acids is neither an exaggerated demand nor technical marketing. It is a fundamental requirement that separates professional processes from problem operations.

What the 2% Difference Is Made Of

When we compare an acid at 93% purity with one at 98%, the difference goes beyond the 5 percentage points. It lies in what makes up the remaining 5%.

Critical Impurities

The percentage points missing to reach 100% are not inert. In lower-purity acids, we find:

Iron: Incorporated into the surface during pickling, it causes dark stains in precious metal baths.

Copper: Contaminates subsequent processes and compromises adhesion.

Unwanted chlorides: Affect bath stability and cause corrosion.

Organic matter: Reduces efficiency and contaminates parts.

The Three Essential Acids

Boreto & Cardoso®, with 53 years of experience since 1972, works with three fundamental acids for jewelry electroplating.

1. Hydrochloric Acid

Application: Pickling and activation of metal surfaces.

Technical specifications:

  • Concentration: 37% (±0.5%)
  • Minimum purity: 98%
  • Iron and copper: Absent
  • Appearance: Completely colorless liquid

Why purity matters: Impurities are incorporated into the surface during pickling and cause stains in the precious metal baths that follow. Lower purity compromises final quality.

Simple visual test: Pure acid is completely colorless. A yellowish tint indicates iron contamination.

2. Nitric Acid

Application: Selective pickling, stainless steel cleaning, passivation.

Technical specifications:

  • Concentration: 65%
  • Purity: Minimum 98%
  • Chloride content: Maximum 0.003%
  • Color: Colorless to slightly yellowish

Specific applications: Silver cleaning, stainless steel pickling, preparation for rhodium baths.

3. Sulfuric Acid

Application: Electrolyte in baths, acid activation, solution preparation.

Technical specifications:

  • Concentration: 98%
  • Purity: Above 99%
  • Organic matter: Absent
  • Heavy metals: Minimal

Key point: A direct component of plating baths. Purity directly affects bath life and stability.

Direct Impact on Processes

Surface Preparation

Pickling with acids of adequate purity removes oxides evenly. Contaminated acids leave residues that compromise later stages.

Plating Baths

When acids are direct components of the baths (as with sulfuric acid), impurities build up and progressively degrade quality.

Adhesion

Surfaces prepared with contaminated acids show poor adhesion. Parts peel or blister after a short time.

How to Verify Purity

Mandatory Documentation

The lot-specific certificate of analysis must state:

  • Exact percentage purity
  • Content of the main contaminants (Fe, Cu, Cl)
  • Analytical method used
  • Identified technical officer

Visual Test

Pure hydrochloric acid is completely colorless. A yellowish tint indicates iron contamination, and the lot should be rejected.

Traceability

The lot number on the packaging must match the certificate provided. Generic certificates have no technical or legal value.

Reliable Suppliers

What to Look For

Strict quality control: Suppliers with a technical structure ensure real control.

Renowned brands: Boreto & Cardoso® works exclusively with manufacturers that maintain strict standards.

Certification by lot: Every lot received must have a specific certificate, not a generic one.

Full traceability: A system that lets you look up the history of each lot.

The Boreto & Cardoso® Experience

With 53 years serving the Brazilian market, Boreto & Cardoso® has developed strict criteria for selecting suppliers. We only work with acids that meet a minimum purity of 98%, and we provide lot-specific certification.

Consequences of Inadequate Purity

Common Problems

Stains in precious metal baths: Iron in the acid contaminates the gold bath and causes dark stains.

Poor adhesion: A poorly prepared surface results in premature peeling.

Shorter service life: Contaminated baths degrade faster.

Constant rework: Rejected parts generate significant costs.

The Real Cost

The "good price" of lower-purity acids turns into a loss once rework, production stoppages and nonconformities are added up.

Technical Grade vs. Analytical Grade

Technical Grade

Purity: 95-98% Application: General electroplating processes Cost: Baseline

Analytical Grade

Purity: >99% Application: Baths that directly incorporate precious metals Cost: Higher, justified in critical applications

Recommendation

For professional jewelry electroplating, technical grade with a minimum purity of 98% meets most applications. Analytical grade is reserved for precious metal baths in which the acid is a direct component.

Proper Storage

Even high-purity acids degrade if stored improperly.

Ideal Conditions

Temperature: 15-30°C Humidity: <70% Sun exposure: None Ventilation: Adequate Floor: Impermeable, with containment

Segregation

Acids must be stored away from alkalis. Accidental mixing causes a dangerous reaction.

Documentation and Compliance

Up-to-date SDS

A Safety Data Sheet compliant with ABNT NBR 14725:2019 (the Brazilian standard for chemical hazard communication) is mandatory. An outdated SDS is a frequent cause of fines.

Specific Certificates

Each lot must have its own certificate with the analyses of that specific lot. Generic certificates, or identical certificates for different lots, indicate inadequate traceability.

Organized Records

Documentation must be kept for at least 5 years to satisfy environmental audits and certifications.

Trends for 2025

Digital Traceability

QR codes on packaging will provide immediate access to certificates and the complete history of the lot.

On-Site Analysis

Portable equipment will allow purity to be validated at receipt, reducing dependence on external laboratories.

On-Demand Supply

Scheduled deliveries will reduce the need for large inventories, keeping products always within their ideal shelf life.

Verification Checklist

When Receiving Acids

  • Purity meets the 98% minimum
  • Concentration as specified
  • Correct visual appearance (colorless for hydrochloric)
  • Certificate matches the lot on the packaging
  • Lot number visible and legible
  • Manufacturing and expiry dates clearly shown
  • Up-to-date SDS provided
  • Packaging intact and undamaged

For Suppliers

  • Works with renowned brands
  • Provides lot-specific certificates
  • Has a traceability system
  • SDS compliant with ABNT NBR 14725:2019
  • Verifiable references in the sector

Conclusion

A minimum purity of 98% in electroplating acids is no technical exaggeration. It is a fundamental specification that protects your investment in precious metals, ensures final quality and avoids constant rework.

Boreto & Cardoso®, with 53 years of experience since 1972, works exclusively with acids that strictly meet this specification, providing lot-specific certification and complete documentation in line with current legislation.

Contact Us

Boreto & Cardoso® Ltda

📞 Headquarters: (11) 3931-1722, (11) 2366-6260, WhatsApp (11) 99108-2229, (19) 97685-0233 📞 Limeira Branch: (19) 99458-6331 📱 Branch WhatsApp: (19) 99557-1693 📧 boreto@boreto.com.br

📍 Headquarters: R. Alagoas, 30, Santana de Parnaíba/SP, 06530-245 📍 Branch: R. Aratibá, 759, Limeira/SP, 13481-208

🕐 Monday to Friday: 8:00 a.m. to 12:00 p.m. and 1:15 p.m. to 5:30 p.m.

Boreto & Cardoso®: 53 years ensuring purity and quality in chemical inputs for electroplating.

Note to the reader

This article brings together technical information drawn from different sources, with the aim of broadening knowledge about the raw materials mentioned.

It is for information purposes only and does not constitute any indication of application, formulation or direct recommendation for use on the part of Boreto & Cardoso.

Boreto & Cardoso®, with 53 years of experience, operates strictly as a supplier of chemical inputs for a wide range of applications, and each user is responsible for verifying the suitability and compliance of their own application.