A cosmetics plant replaces a worn mixer shaft with a locally made part. It fits, it turns, and production restarts. Two months later, the quality team finds faint rust streaks inside a batch tank and traces of discoloration in a white cream. The replacement shaft was machined from the wrong stainless grade, and its surface was left with deep tool marks that trapped product between cleaning cycles. In cosmetic production, a part can be dimensionally correct and still be wrong. Stainless steel parts for cosmetic machinery have to meet hygiene requirements as well as drawings.
Why Cosmetic Equipment Is Different
Creams, lotions, and gels are often water-based, sometimes acidic or salty, and frequently contain fragrances and preservatives that are chemically active. Equipment is cleaned regularly with hot water, detergents, and sanitizers. Every surface that touches product must resist corrosion, avoid contaminating the product, and be easy to clean completely.
Choosing the Stainless Grade
| Grade | Strengths | Where it fits |
|---|---|---|
| SUS304 (AISI 304) | Good general corrosion resistance; widely available; economical | Frames, covers, non-contact parts, mild products |
| SUS316 / 316L (AISI 316) | Molybdenum improves resistance to chlorides and acids; 316L is better for welded parts | Product-contact parts: shafts, impellers, pump components, tank fittings |
| SUS420 / SUS440C | Can be hardened for wear resistance | Wear parts such as some seals, valve seats, or cutting elements, where corrosion exposure is moderate |
For most product-contact parts, 316 or 316L is the safer choice. 304 is often used to save cost, but it is more vulnerable to pitting from salty formulations and chloride-based cleaning agents.
Surface Finish Is a Hygiene Specification
A rough surface has valleys where product and bacteria can hide from cleaning. In hygienic equipment, surface roughness on product-contact parts is typically specified as a maximum Ra value, often below 0.8 µm, and lower for critical surfaces. That usually means fine turning followed by grinding or polishing, not just a standard machined finish.
Equally important: no sharp internal corners, no crevices, no blind threads in product zones, and no gaps between parts where product can collect.
Fits in Pumps and Mixers
Liquid transfer pumps and mixers depend on close running clearances between rotors, impellers, and housings. Too much clearance and the pump loses pressure or the mixer loses shear. Too little and stainless parts can gall (adhesive wear where two stainless surfaces seize together). Galling is a known risk with stainless-on-stainless contact, so clearances, surface finish, and sometimes material pairing must be chosen with care.
Machining Stainless Properly
Austenitic stainless steels such as 304 and 316 work-harden as they are cut. If the tool rubs instead of cutting, the surface becomes hard and difficult to finish. That requires sharp tools, sufficient feed, and stable setups. After machining, parts should be cleaned of any iron contamination from tools or handling, since embedded iron particles can rust and mark the surface.
How Merdeka Precision Supports Cosmetic Manufacturers
The cosmetic industry is one of the sectors we serve. Our job order products include parts such as a cosmetic cream mixer and a liquid transfer pump for cosmetic cream, made to customer specifications.
These parts are produced through our fabrication service: a part drawing is received or created, material is prepared (supplied by us or by the customer), and the part is machined on our lathes, milling machines, and machining center, then ground where finish requires it. Every part passes QC inspection with calibrated instruments before delivery under our ISO 9001:2015 quality system.
What to Tell Your Supplier
- Which surfaces contact product
- The stainless grade required, and whether welding is involved
- Required surface roughness on product-contact areas
- The cleaning agents and temperatures the part will see
- Running clearances for rotating parts
Are the replacement parts in your mixing and filling lines specified to the same hygiene standard as the original equipment? Share your drawing or sample and we will review grade and finish with you before machining.