Skip to content
LexBuild

40 CFR § 420.91 - Specialized definitions. 

---
identifier: "/us/cfr/t40/s420.91"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 420.91 - Specialized definitions."
title_number: 40
title_name: "Protection of Environment"
section_number: "420.91"
section_name: "Specialized definitions."
chapter_name: "ENVIRONMENTAL PROTECTION AGENCY"
subchapter_number: "N"
subchapter_name: "EFFLUENT GUIDELINES AND STANDARDS"
part_number: "420"
part_name: "IRON AND STEEL MANUFACTURING POINT SOURCE CATEGORY"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
authority: "33 U.S.C. 1311, 1314, 1316, 1317, 1318, 1342, and 1361."
regulatory_source: "47 FR 23284, May 27, 1982, unless otherwise noted."
cfr_part: "420"
---

# 420.91 Specialized definitions.

(a) The term *sulfuric acid pickling* means those operations in which steel products are immersed in sulfuric acid solutions to chemically remove oxides and scale, and those rinsing operations associated with such immersions.

(b) The term *hydrochloric acid pickling* means those operations in which steel products are immersed in hydrochloric acid solutions to chemically remove oxides and scale, and those rinsing operations associated with such immersions.

(c) The term *combination acid pickling* means those operations in which steel products are immersed in solutions of more than one acid to chemically remove scale and oxides, and those rinsing steps associated with such immersions.

(d) The term *fume scrubber* means those pollution control devices used to remove and clean fumes originating in pickling operations.

(e) The term *batch* means those pickling operations which process steel products such as coiled wire, rods, and tubes in discrete batches or bundles.

(f) The term *continuous* means those pickling operations which process steel products other than in discrete batches or bundles.

(g) The term *acid recovery* means those sulfuric acid pickling operations that include processes for recovering the unreacted acid from spent pickling acid solutions.

(h) The term *acid regeneration* means those hydrochloric acid pickling operations that include processes for regenerating acid from spent pickling acid solutions.

(i) The term *neutralization* means those acid pickling operations that do not include acid recovery or acid regeneration processes.

(j) The term *spent acid solution* (or spent pickle liquor) means those solutions of steel pickling acids which have been used in the pickling process and are discharged or removed therefrom.

(k) The term *rod, wire and coil* means those acid pickling operations that pickle rod, wire or coiled rod and wire products.

(l) The term *bar, billet and bloom* means those acid pickling operations that pickle bar, billet or bloom products.

(m) The term *strip, sheet and plate* means those acid pickling operations that pickle strip, sheet or plate products.

(n) The term *pipe, tube and other* means those acid pickling operations that pickle pipes, tubes or any steel product other than those included in paragraphs (k), (l) and (m) of this section.